Showing papers in "Journal of Polymer Science Part A in 1999"
TL;DR: The story of the discovery and development of onium salt photoinitiators for cationic polymerization is chronicled in this article, and the mechanisms of their initiation are discussed briefly.
Abstract: The story of the discovery and development of onium salt photoinitiators for cationic polymerization is chronicled. The chemistry of the synthesis of these compounds is outlined, and the mechanisms of their initiation are discussed briefly. Among the most useful of these types of photoinitiators are diaryliodonium and triarylsulfonium salts, which are used widely for photoinduced cationic crosslinking reactions. From the very beginning, onium salt photoinitiated cationic polymerizations have found use in a multitude of practical applications. Specifically discussed in this article are the use of onium salts in coatings, adhesives, printing inks, release coatings, stereolithography, holographic recording, photocurable composites, and microelectronic photoresists. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4241–4254, 1999
435 citations
TL;DR: The synthetic strategies available for the synthesis of miktoarm star (μ-star) polymers with molecular weight, chemical, or topological asymmetry are reviewed in this article.
Abstract: The synthetic strategies available for the synthesis of miktoarm star (μ-star) polymers with molecular weight, chemical, or topological asymmetry are reviewed. All strategies are based on functional living polymer chains and linking agents. Although each strategy has its weak and strong points, it seems that anionic polymerization combined with chlorosilane methodology yields the widest variety of model single and double μ-stars. These novel architectures open new horizons in polymer science and technology. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 857–871, 1999
347 citations
TL;DR: In this article, the basic kinetic features of living polymerizations controlled and regulated by persistent radicals or related species and by reversible atom transfer are described, and analytical equations for the polymerization rates and for the polydispersities of the resulting polymers are presented, and important requirements for reaction rate constants leading to control are outlined.
Abstract: We describe the basic kinetic features of “living” polymerizations controlled and regulated by persistent radicals or related species and by reversible atom transfer. In these systems a special kinetic phenomenon operates—the Persistent Radical Effect. It is also known from selective organic syntheses and reflects a self-inhibition of the termination reaction. Analytical equations for the polymerization rates and for the polydispersities of the resulting polymers are presented, and important requirements for reaction rate constants leading to control are outlined. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1885–1901, 1999
325 citations
TL;DR: In this article, a solution polycondensation of di-p-toluenesulfonic acid salts of bis-(α-amino acid) α, α,ω-alkylene diesters and di- p-nitrophenyl esters of diacids was studied to assess the effect of these new polymers on their biodegradation properties.
Abstract: The purpose of this research was to synthesize new regular poly(ester amide)s (PEAs) consisting of nontoxic building blocks like hydrophobic α-amino acids, α,ω-diols, and aliphatic dicarboxylic acids, and to examine the effects of the structure of these building block components on some physico-chemical and biochemical properties of the polymers. PEAs were prepared by solution polycondensation of di-p-toluenesulfonic acid salts of bis-(α-amino acid) α,ω-alkylene diesters and di-p-nitrophenyl esters of diacids. Optimal conditions of this reaction have been studied. High molecular weight PEAs (Mw = 24,000–167,000) with narrow polydispersity (Mw/Mn = 1.20–1.81) were prepared under the optimal reaction conditions and exhibited excellent film-forming properties. PEAs obtained are mostly amorphous materials with Tg from 11 to 59°C. α-Chymotrypsin catalyzed in vitro hydrolysis of these new PEA substrates was studied to assess the effect of the building blocks of these new polymers on their biodegradation properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 391–407, 1999
283 citations
TL;DR: The ureido-pyrimidone network as mentioned in this paper is the first example of a truly reversible polymer network showing these features, and it can be used to construct supramolecular materials possessing acceptable mechanical properties.
Abstract: The strong dimerizing, quadruple hydrogen-bonding ureido-pyrimidone unit is used to obtain reversible polymer networks. A new synthetic route from commercially available starting materials is described. The hydrogen-bonding ureido-pyrimidone network is prepared using 3(4)-isocyanatomethyl-1-methylcyclohexyl-isocyanate (IMCI) in the regioselective coupling reaction of multi-hydroxy functionalized polymers with isocytosines. 1H- and 13C-NMR, IR, MS, and ES-MS analysis, performed on a model reaction using butanol, demonstrated the formation of the hydrogen-bonding ureido-pyrimidone unit in a yield of more than 95%. The well-defined, strong hydrogen-bonding ureido-pyrimidone network is compared with a traditional covalently bonded polymer network, a multi-directional hydrogen-bonded polymer network based on urea units, and a reference compound. The advantage of the reversible, hydrogen-bonded polymer networks is the formation of the thermodynamically most favorable products, which show a higher “virtual” molecular weight and shear modulus, compared to the irreversible, covalently bonded polymer network. The properties of the ureido-pyrimidone network are unique; the well-defined and strong dimerization of the ureido-pyrimidone unit does not require any additional stabilization such as crystallization or other kinds of phase separation, and displays a well-defined viscoelastic transition. The ureido-pyrimidone network represents the first example of a truly reversible polymer network showing these features. Furthermore, the ureido-pyrimidone dimerization is strong enough to construct supramolecular materials possessing acceptable mechanical properties. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3657–3670, 1999
260 citations
TL;DR: This article describes the recent progress of enzymatic polymerization technique, developed mainly during this decade, which utilizes enzymes of hydrolases and oxidoreductases as catalysts.
Abstract: Enzymatic polymerization denotes an in vitro polymerization via nonbiosynthetic pathways catalyzed by an isolated enzyme. This article describes the recent progress of this polymerization technique, developed mainly during this decade. The polymerization utilizes enzymes of hydrolases and oxidoreductases as catalysts. This new method of polymer synthesis provided natural polysaccharides like cellulose, amylose, xylan, and chitin, and unnatural polysaccharides catalyzed by a glycosidase from well-designed monomers, various functionalized polyesters catalyzed by lipase from a variety of monomers, and polyaromatics materials catalyzed by an oxidoreductase and an enzyme model complex from phenols and anilines. An oxidoreductase also initiated vinyl polymerizations. Characteristic features of enzymatic polymerizations are discussed, including the importance of the combination of substrate monomer and enzyme. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3041–3056, 1999
237 citations
TL;DR: In this paper, the reaction of 3,4-dihydro-3,6-dimethyl-2H-1,3-benzoxazine using strong and weak carboxylic acids and phenols as catalysts has been studied using Fourier transform infrared (FTIR) spectroscopy.
Abstract: The reaction of 3,4-dihydro-3,6-dimethyl-2H-1,3-benzoxazine using strong and weak carboxylic acids and phenols as catalysts has been studied using Fourier transform infrared (FTIR) spectroscopy. The auto-accelerated curing using sebacic acid as catalyst is further documented using 1H-nuclear magnetic resonance (NMR) and dielectric analysis. Termination of curing, using strong acids or no catalyst, are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1913–1921, 1999
215 citations
TL;DR: Using excessively loaded propylene oxide (PO) as a solvent, the copolymerization of carbon dioxide (CO2) and PO was carried out with zinc glutarate catalyst, consequently producing poly(propylene carbonate) of high molecular weight in a high yield as discussed by the authors.
Abstract: Using excessively loaded propylene oxide (PO) as a solvent, the copolymerization of carbon dioxide (CO2) and PO was carried out with zinc glutarate catalyst, consequently producing poly(propylene carbonate) of high molecular weight in a high yield (64–70 g polymer per gram of catalyst) never achieved before. Both the PO used as solvent and the excessively loaded CO2 were fully recoverable, respectively, and reusable for their copolymerization, indicating that this is a clean, green polymerization process to convert CO2 to its polycarbonate. The polymer yield was further improved by scaling up the copolymerization process. Among zinc glutarate catalysts prepared through several synthetic routes, one from zinc oxide delivered the highest yield in the copolymerization. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1863–1876, 1999
190 citations
TL;DR: In this paper, a segmented polyurethane/clay nanocomposite based on poly(caprolactone), diphenylmethane diisocyanate, butanediol, and poly(Caprolacton)/clay prepolymer was synthesized as evidenced by FTIR and X-ray diffraction studies.
Abstract: A novel segmented polyurethane/clay (PU/clay) nanocomposite based on poly(caprolactone), diphenylmethane diisocyanate, butanediol, and poly(caprolactone)/clay prepolymer was synthesized as evidenced by FTIR and X-ray diffraction studies. Poly(caprolactone)/clay (PCL/clay) prepolymer was first synthesized in a nanocomposite form as confirmed by X-ray diffraction. X-ray diffraction study showed that PU/clay contained crystalline structure due to the presence of PCL/clay. In mechanical properties, about 1.4% PCL/clay in PU/clay resulted in a large increase in the elongation of PU/clay. However, when the amount of PCL/clay was 4.2%, the elongation of PU/clay was reduced drastically. This behavior indicated that PU/clay can be transformed from an elastomer to a thermoplastic material as the amount of PCL/clay in PU/clay increased. Additionally, the lap shear stress of PU/clay was at least three times that of neat PU as a result of the PCL/clay component. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2225–2233, 1999
172 citations
TL;DR: In this article, the authors compared the cure behavior and properties of phthalonitrile polymers derived from three different monomers, namely, 4,4′-bis(3,4-dicyanophenoxy)biphenyl, 2,2-bis[4,4]-hexafluoropropane and 2.2]-propane, and showed that the char yields are high and the total heat release upon exposure to 50 kW/m2 flux for each polymer is low, compared to other thermosets.
Abstract: This article compares the cure behavior and properties of phthalonitrile polymers derived from three different monomers, namely, 4,4′-bis(3,4-dicyanophenoxy)biphenyl, 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]hexafluoropropane and 2,2-bis[4-(3,4-dicyanophenoxy)phenyl]propane. Rheometric measurements with monomer melt in the presence of an aromatic diamine curing agent reveal that the rate of the cure reaction differs for the three monomers. The rate is dependent on the concentration of the curing agent. The glass transition temperature advances with increasing extent of cure and disappears upon postcure at temperatures in excess of 350°C. Based on thermogravimetric analysis, the thermal stability of all three polymers are comparable, whereas the fluorine-containing resin shows the best oxidative stability at elevated temperatures. Microscale calorimetric studies on all three polymers reveal that the char yields are high and the total heat release upon exposure to 50 kW/m2 flux for each polymer is low, compared to other thermosets. Flexural strength ranges between 80–120 MPa. The water uptake under ambient conditions is less than 3% by weight after submersion in water for seven months. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2105–2111, 1999
160 citations
TL;DR: In this paper, a novel phosphorus-containing epoxy resins (1-3% phosphorus content) were synthesized by the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and the diglycidyl ether of bisphenol A and then cured with 4,4′-diaminodiphenyl sulfone or phenol novolac.
Abstract: Novel phosphorus-containing epoxy resins (1–3% phosphorus content) were synthesized by the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO) and the diglycidyl ether of bisphenol A and then cured with 4,4′-diaminodiphenyl sulfone or phenol novolac. Differential scanning calorimetry, high performance liquid chromatography, and epoxide equivalent weight titration were used to trace the reaction between the DOPO and the epoxy. The thermal stability and flame retardancy were checked by thermal gravimetric analysis, the limiting oxygen index, and the UL-94 vertical test. The glass transitions were measured by dynamic mechanical analysis. The relation between these properties (thermal stability, flame retardancy, and glass transition) and the DOPO contents (phosphorus content) were discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3903–3909, 1999
TL;DR: The design and synthesis of a new dendrimer–poly(ethylene glycol) (PEG) conjugate that may be used as a model drug carrier and characterized by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry.
Abstract: The design and synthesis of a new dendrimer–poly(ethylene glycol) (PEG) conjugate that may be used as a model drug carrier are described. The starting material is a polyether dendrimer with two different types of chain end functionalities. The dendritic assembly is made water soluble through attachment of short PEG chains to the dendrimer via one type of functionality. The remaining chain end functionalities then were used to incorporate model drug molecules of varying polarity into the modified dendrimer. Cholesterol and two amino acid derivatives were selected as model drugs for attachment through their respective hydroxyl, carboxylic acid, and amino functional groups to the dendrimer via carbonate, ester, and carbamate linkages. The resulting water-soluble dendrimer-model drug conjugates were characterized by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3492–3503, 1999
TL;DR: In this article, the authors used the concept of multicenter catalysis with different centers that respond differently to changes in reaction parameters and proposed a new reaction scheme based on a hypothesis that the Ti-C2H5 bond in active centers has low reactivity due to the equilibrium formation of a Ti-H5 species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center.
Abstract: Kinetics of ethylene homopolymerization reactions and ethylene/1-hexene copolymerization reactions using a supported Ziegler–Natta catalyst was carried out over a broad range of reaction conditions. The kinetic data were analyzed using a concept of multicenter catalysis with different centers that respond differently to changes in reaction parameters. The catalyst contains five types of active centers that differ in the molecular weights of material they produce and in their copolymerization ability. In ethylene homopolymerization reactions, each active center has a high reaction order with respect to ethylene concentration, close to the second order. In ethylene/α-olefin copolymerization reactions, the centers that have poor copolymerization ability retain this high reaction order, whereas the centers that have good copolymerization ability change the reaction order to the first order. Hydrogen depresses activity of each type of center in the homopolymerization reactions in a reversible manner; however, the centers that copolymerize ethylene and α-olefins well are not depressed if an α-olefin is present in the reaction medium. Introduction of an α-olefin significantly increases activity of those centers, which are effective in copolymerizing it with ethylene but does not affect the centers that copolymerize ethylene and α-olefins poorly. To explain these kinetic features, a new reaction scheme is proposed. It is based on a hypothesis that the Ti—C2H5 bond in active centers has low reactivity due to the equilibrium formation of a Ti—C2H5 species with the H atom in the methyl group β-agostically coordinated to the Ti atom in an active center. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4255–4272, 1999
TL;DR: In this article, the authors reported the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary esters linkages, that are thermally degradable below 300 °C.
Abstract: In flip-chip technology, the development of reworkable underfill materials has been one of the keys to the recovery of highly integrated and expensive board assembly designs through the replacement of defective chips. This article reports the syntheses, formulations, and characterizations of two new diepoxides, one containing secondary ester linkages and the other containing tertiary ester linkages, that are thermally degradable below 300 °C. The secondary and tertiary ester diepoxides were synthesized in three and two steps, respectively. Both compounds were characterized with NMR and Fourier transform infrared spectroscopy and formulated into underfill materials with an anhydride as the hardener and an imidazole as the catalyst. A dual-epoxy system was also formulated containing the tertiary ester diepoxide and a conventional aliphatic diepoxide, 3,4-epoxy cyclohexyl methyl-3,4-epoxycyclohexyl carboxylate (ERL-4221E), with the same hardener and catalyst. The curing kinetics of the formulas were studied with differential scanning calorimetry (DSC). Thermal properties of cured samples were characterized with DSC, thermogravimetric analysis, and thermomechanical analysis. The dual-epoxy system showed a viscosity of 18.7 and 0.87 P at 25 and 100 °C, respectively. The cured secondary, tertiary, and dual-epoxy formulas showed decomposition temperatures around 265, 190, and 220 °C, glass-transition temperatures around 120-140, 110-157, and 140-157 °C, and coefficients of thermal expansion of 70, 72, and 64 ppm/°C below their glass-transition temperatures, respectively. The shear strength of the cured dual-epoxy system decreased quickly with aging at 230 °C. The reworkability test showed that the removal of a chip underfilled with this material from the board was quite easy, and the residue on the board could be thoroughly removed with a mechanical brush without obvious damage to the solder mask. In summary, the synthesized tertiary epoxide can be used as a reworkable underfill for flip-chip applications.
TL;DR: In this paper, the authors investigated the thermoprecipitation of two macromolecule structures, poly(N-isopropylacrylamide) (poly-NIPA), from aqueous solution.
Abstract: The paper investigates the thermoprecipitation of two macromolecule structures, poly(N-isopropylacrylamide) (poly-NIPA) and poly(N,N-diethylacrylamide) (poly-DEA) from aqueous solution. The majority of the data are collected for small (M w < 5000 g/mol) homogeneous (D < 1.3) molecules of the indicated type synthesized by anionic, group transfer, and radical polymerization in the presence of a chain transfer agent. Conventional radical polymers (M w < 200,000 g/mol) are also synthesized and used for comparison. Turbidity curves (photometry) and transition enthalpies (high sensitivity differential scanning calorimetry) are measured to investigate the phase transition as a function of the molecular size and the tacticity as well as the concentration of certain solution additives (simple salts, glucose, and the surfactant tetrabutylammonium acetate) and mixtures thereof. Where applicable, the results are interpreted on the basis of a two-state model to gain insight in the cooperativity of the transition.
TL;DR: In this article, maleic anhydride (MAn) was grafted onto aliphatic and aromatic/aliphatic copolyesters by reactive extrusion in the presence of a free radical initiator using a twin-screw extruder.
Abstract: Maleic anhydride (MAn) was grafted onto aliphatic and aromatic/aliphatic copolyesters by reactive extrusion in the presence of a free radical initiator using a twin-screw extruder. The grafting reaction was confirmed by spectroscopic analyses. The presence of succinic anhydride groups was shown by FT-IR spectroscopy, and NMR spectra indicate that the grafts consist of single succinic anhydride units. The 2D 1H-NMR spectra (COSY) indicate that grafting reactions take place at aliphatic dicarboxylic acid units of copolyesters. The graft content was determined by a nonaqueous titration method. The effects of concentration of initiator and monomer and reaction temperature on the graft content and intrinsic viscosity were studied. The low percentage grafting in poly(lactic acid) was observed due to the presence of limited free radical sites in the polymer backbone. Temperature and monomer and initiator concentrations affect the graft content, and the desired graft content with minimal degradation can be obtained by controlling these factors. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1693–1702, 1999
TL;DR: In this article, a hexameric phenyl-ethynyl macrocycle was prepared by statistical cyclization of the copper salt of m-iodo-phenylacetylene in 4.6% yield.
Abstract: It has been about 25 years since Staab prepared a hexameric phenyl–ethynyl macrocycle by the statistical cyclization of the copper salt of m-iodo-phenylacetylene in 4.6% yield. Since that time, different methodologies have been investigated that allow not only the preparation of selectively functionalized structures, but also their formation in high yields. The repetitive formation of precursors followed by an intramolecular cyclization is only one approach to these structures. Alternatives include the use of covalently or noncovalently bound templates, as well as cyclization under thermodynamic control. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2685–2698, 1999
TL;DR: In this article, a ring-opening poly(ethylene oxide)-b-poly(L-lactic acid)-co-glycolic acid (PEO-PLLA) diblock copolymers were synthesized via a ring opening polymerization from poly(methylene oxide) and L-lactide.
Abstract: Poly(ethylene oxide)-b-poly(L-lactic acid) (PEO-PLLA) diblock copolymers were synthesized via a ring opening polymerization from poly(ethylene oxide) and L-lactide. Stannous octoate was used as a catalyst in a solution polymerization with toluene as the solvent. Their physicochemical properties were investigated by using infrared spectroscopy, 1 H-NMR spectroscopy, gel permeation chromatography, and differential scanning calorimetry, as well as the observational data of gel-sol transitions in aqueous solutions. Aqueous solutions of PEO-PLLA diblock copolymers changed from a gel phase to a sol phase with increasing temperature when their polymer concentra- tions are above a critical gel concentration. As the PLLA block length increased, the gel-sol transition temperature increased. For comparison, diblock copolymers of poly- (ethylene oxide)-b-poly(L-lactic acid-co-glycolic acid) (PEO-P(LLA/GA)) and poly(ethyl- ene oxide)-b-poly(DL-lactic acid-co-glycolic acid) (PEO-P(DLLA/GA)) were synthesized by the same methods, and their gel-sol transition behaviors were also investigated. The gel-sol transition properties of these diblock copolymers are influenced by the hydro- philic/hydrophobic balance of the copolymer, block length, hydrophobicity, and stereo- regularity of the hydrophobic block of the copolymer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2207-2218, 1999
TL;DR: In this article, the authors investigated the influence of crosslinker (MBA) and initiator (KPS) concentrations and temperature effects on the polymerization conversion, the particle size, and water-soluble polymer (WSP) as a function of time.
Abstract: Thermosensitive crosslinked polymer latexes have been synthesized by precipitation polymerization of N-isopropylmethacrylamide (NIPMAM) as a main monomer, methylene bis-acrylamide (MBA) as a crosslinker, and potassium persulfate (KPS) as the initiator. Polymerizations kinetics were first investigated by studying both the influence of crosslinker (MBA) and initiator (KPS) concentrations and temperature effects on the polymerization conversion, the particle size, and water-soluble polymer (WSP) as a function of time. Particle size analysis by Scanning Electron Microscopy (SEM) showed that a short nucleation step afforded the synthesis of highly monodispersed latexes. In addition, a strong dependence of WSP formation on MBA and KPS concentration and polymerization temperature was found, as well. Comparison of particle size by SEM and quasielastic light scattering clearly evidenced the dramatic effect of temperature on particle size. Lower critical solubility temperatures (LCST) of latexes were determined and compared. Finally, based on these results, the mechanism of particle formation in this polymerization process is discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1823–1837, 1999
TL;DR: In this article, a head-to-tail regioregularity of poly(3-alkylthiophenes) was investigated by an oxidative coupling polymerization, which is the simplest and easiest way for the synthesis of polythiophenses.
Abstract: We investigated a head-to-tail regioregularity of poly(3-alkylthiophenes) from 3-alkylthiophene by an oxidative coupling polymerization, which is the simplest and easiest way for the synthesis of polythiophenes. The polymerizations were conducted using ferric chloride (III) as an oxidant in chloroform. Investigating the polymerization conditions, a lower temperature and a lower concentration were effective for increasing the head-to-tail (HT) content. The best HT content of 88% was obtained when the temperature was -45°C and the initial monomer concentration was 0.02 mol L -1 . Washing the resulting polymer by n-hexane further increased the content to 91%. Thus, it was found that the high regioselectivity can be achieved by the simple polymerization and the simple operation such as washing. The polymerization mechanism causing the regularity is also discussed.
TL;DR: In this article, the aging of 1,3-diaminopropane (DAP) plasma polymer samples was monitored by XPS and FTIR in order to study how the oxidative reaction pathways might differ in a plasma-deposited material that is initially rich in amine groups.
Abstract: In the course of plasma deposition of organic–polymeric thin films, radicals are incorporated into the growing film. These radicals initiate spontaneous oxidation reactions that continue over many weeks when the plasma polymers are stored in air. These reactions and their products have been previously studied in detail for spectroscopically simple, hydrocarbon-based plasma polymers. In this investigation, the aging of 1,3-diaminopropane (DAP) plasma polymer samples was monitored by XPS and FTIR in order to study how the oxidative reaction pathways might differ in a plasma-deposited material that is initially rich in amine groups. The freshly deposited DAP plasma polymer consisted of a random hydrocarbon network with a considerable amount of unsaturation and a high concentration of nitrogen-containing functional groups, mainly primary/secondary amines and imines. These groups strongly influenced the aging reactions: in contrast to hydrocarbon-based material where hydrogen abstraction and reaction of carbon-centered radicals with in-diffusing oxygen result in a wide range of oxidative products, both XPS and FTIR identified a rather narrow range of products (mainly amides and similar groups) in DAP plasma polymers even after extensive aging for more than 2 years. Reaction routes based on oxidation and/or hydrolysis of nitrogen functional groups, and involving primary as well as secondary reactions, are proposed to account for the spectroscopic data. The structure of the aged DAP plasma polymer appeared to be stable, and did not undergo more extensive oxidation, in contrast to hydrocarbon plasma polymers. In particular, carboxylic acid groups and carbamates were not detected. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2191–2206, 1999
TL;DR: In this paper, the influence of the chemical structure of the monomers on their reactivity has been studied by quantum semi-empirical methods and the polyimides have been characterized by FTIR and by NMR in the case of soluble polymers.
Abstract: New dianhydrides containing t-butyl and phenyl pendant groups have been synthesized and used as monomers, together with commercial diamines, to prepare novel polyimides. The influence of the chemical structure of the monomers on their reactivity has been studied by quantum semiempirical methods. The polyimides have been characterized by FTIR and by NMR in the case of soluble polymers. The presence of pendant groups and the method used to imidize polyimide precursors greatly affected polymer properties such as solubility, glass transition temperature, thermal stability, and mechanical properties. As a rule, the novel polyimides showed better solubility in organic solvents than the parent polyimides. Glass transition temperatures in the range 250 -270°C and decomposition temperatures over 520°C were observed for the set of current polymers. Tensile strengths up to 135 MPa and mechanical moduli up to 3.0 GPa were measured on films of the current polyimides. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 805- 814, 1999
TL;DR: In this article, copolymerization of five mono-vinyl methacrylic monomers including methyl methacrylate (MMA), BMA, BMA with divinylbenzene (DVB), in a wide range of comonomer composition, were carried out in acetonitrile to form mono- or narrow disperse crosslinked copolymers.
Abstract: Precipitation copolymerizations of five mono-vinyl methacrylic monomers including methyl methacrylate (MMA), butyl methacrylate (BMA), dodecyl methacrylate (DMA), glycidyl methacrylate (GMA), and hydroxyethyl methacrylate (HEMA) with divinylbenzene (DVB), in a wide range of comonomer composition, were carried out in acetonitrile to form mono- or narrow disperse crosslinked copolymer microspheres. In addition, two divinyl methacrylic monomers, ethylene glycol dimethacrylate (EGDMA) and triethylene glycol dimethacrylate (TEGDMA), were also copolymerized with DVB, and optionally a third comonomer (GMA or HEMA), to yield similar microspheres in acetonitrile. The possibility of creating porosity was explored for some of the copolymer particles. All these microspheres have clean surfaces due to the absence of any added steric or ionic stabilizer, and they are in the size of the micrometer range, varying from 1 to 7 µm, depending on the type and content of the methacrylic comonomer. Particle size distribution, surface morphology, internal texture, and porosity properties of these particles were studied by a Coulter Multisizer, a scanning electron microscope, a transmission electron microscope, and an Autosorb-1. The effects of comonomers on microsphere formation and morphology are described. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2899–2907, 1999
TL;DR: Unimolecular micelles synthesized from mucic acid, fatty acids, and poly(ethylene glycols) to create biocompatible polymers have great potential as drug carriers.
Abstract: Unimolecular micelles were successfully synthesized from mucic acid, fatty acids, and poly(ethylene glycols) to create biocompatible polymers. These polymers consist of a core-shell structure that resembles conventional micellar structures but with significant thermodynamic stability in aqueous media. The core of the polymers provide a hydrophobic environment for drug encapsulation via hydrophobic interactions, whereas the shell provides excellent water solubility. The polymers were characterized by nuclear magnetic resonance, infrared and mass spectroscopies, as well as gel permeation chromatography, differential scanning calorimetry, and thermogravimetric and elemental analyses. Encapsulation ability was measured using high-pressure liquid chromatography to monitor lidocaine, a hydrophobic molecule. Encapsulation capabilities increased as lipophilicity of the core increased. To verify that encapsulation was caused by individual unimolecular micelles, surface tension and dynamic light scattering measurements were performed. The results indicated that these unimolecular micelles have great potential as drug carriers.
TL;DR: In this paper, the PANI-Naphthal-enesulfonic acid (NSA) was used as a dopant for the synthesis of PANI microtubules.
Abstract: Conducting microtubules of Polyaniline (PANI) were synthesized for the first time by the “in situ doping polymerization” method in the presence of β-naphthal- enesulfonic acid (NSA) as dopant. Different doping methods, such as “immerse doping” and “grind doping,” and different synthetic conditions, such as molar ratio of aniline (An) to NSA (An/NSA), concentration of NSA in the polymerization media, reaction temperature, and time were investigated to understand the formation of microtubules. It was found that the PANI–NSA microtubules can be formed only by the “in situ doping polymerization” method, and the above synthetic conditions strongly affect the formation of the PANI–NSA microtubules, especially the molar ratio of An to NSA. An optimal condition was found under which tubules with 1–3 μm in diameter and 10–50 μm in length were obtained. The morphology of PANI–NSA tubules was proved by SEM and TEM, and their backbone structure was characterized by FTIR, UV-VIS, XPS, and X-ray diffraction. Results of these measurements showed that the molecular structures of the resulted PANI–NSA microtubules were identical to that of PANI–HCl synthesized by conventional method. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 151–157, 1999
TL;DR: In this article, a doped polyaniline (PANI) was synthesized by an in situ doping polymerization method in the presence of different sulfonic acids, such as methanesulfonic acid (MSA), p-methylbenzene sulfonic acid(MBSA), β-naphthalenesulfonic acids (β-NSA), α-Naphthalene ring (α-NSA), 1,5 naphthalenedisulfonic amino acid (1,5-NSA) and 2,4-dinitronaphol
Abstract: Doped polyaniline (PANI) was synthesized by an “in situ doping polymerization” method in the presence of different sulfonic acids, such as methanesulfonic acid (MSA), p-methylbenzene sulfonic acid (MBSA), β-naphthalenesulfonic acid (β-NSA), α-naphthalenesulfonic acid (α-NSA), 1,5-naphthalenedisulfonic acid (1,5-NSA), and 2,4-dinitronaphol-7-sulfonate acid (NONSA). Morphology, solubility in m-cresol, and electrical properties of the doped PANI were measured with the variation of the molecular structure of the selected sulfonic acids. Granular morphology was obtained when the sulfonic acids without a naphthalene ring, such as MSA and MBSA, were used. Regular tubular morphology was obtained only when β-NSA was used. The tubular morphology can be modified by changing the substitutes, the number, and location of sulfo-group(SOH) on the naphthalene ring. These results indicated that naphthalene ring in the selected sulfonic acids plays an important role in forming the tubular morphology of the doped PANI by the “in situ doping polymerization” method. All resulting PANI salts were soluble in m-cresol, with the solubility depending on the molecular structure of the selected dopants. Room-temperature conductivity for the doped PANI ranges from 10−1 to 100S/cm. Temperature dependence of conductivity shows a semiconductor behavior, and it can be expressed by one dimenson Variable Range Hopping (VRH) model. 1 © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1277–1284, 1999
TL;DR: The tortuous road to living carbocationic polymerization is chronicled in this paper, where the authors show a three-step progression to the discovery of 1) controlled initiation, 2) reversible termination (quasiliving systems), and 3) controlled chain transfer.
Abstract: The tortuous road to living carbocationic polymerizations is chronicled. The impetus for this project was my conviction that, just as living anionic polymerizations have started with a critical insight, a similar breakthrough will also be possible with cations. Upon retrospect, the facts show a three-step progression to the objective: Discovery of 1) controlled initiation, 2) reversible termination (quasiliving systems), and 3) controlled chain transfer. But what good is the discovery of a process without demonstrating its usefulness in terms of desirable products? Thus, a section concerns unique microarchitectures obtainable only by this technique: functional liquids, telechelics, thermoplastic elastomers, etc. The marketing of some of these products has already started, and the fundamental exploration of the promises of this technique is in progress worldwide. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2285–2293, 1999
TL;DR: In this article, the surface of polypropylene (PP) films in the presence of various combinations of ultraviolet light and ozone gas (UVO) conditions were studied, and it was found that reaction 1 dominates initially, but its rate is reduced by the formation of products from reaction 2.
Abstract: Chemical reactions of the surface of a polypropylene (PP) film in the presence of various combinations of ultraviolet light and ozone gas (UVO) conditions were studied. Exposure of the polymer surface was carried out in a laboratory-scale UVO reactor in which the following parameters could be varied: ozone concentration, wavelength of ultraviolet (UV) radiation, pulsed operation of the UV lamps, the treatment distance between the PP film and the lamps, and water vapor concentration. Advancing and receding contact angle measurements were used to monitor surface energy changes imparted by the treatment. Two spectroscopic techniques, X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR–FTIR), were used to monitor changes in the polymer surface chemistry. Oxidation of the PP surface is proposed to occur through two alternate mechanisms: (1) insertion of an O (1D) atom to form ether linkages, or (2) hydrogen abstraction by O (3P), followed either by crosslinking or by reaction with oxygen species to form carbonyl and/or carboxyl functional groups. It was found that reaction 1 dominates initially, but that its rate is reduced by the formation of products from reaction 2. It appears that the ether functional groups produced by reaction 1 are responsible primarily for increased surface energy. Carbonyl, carboxyl, and hydroxyl groups formed in reaction 2 appear to have little additional effect on surface energy; it is proposed that these groups are involved strongly in intramolecular hydrogen bonding, thereby decreasing their availability to contribute to increased surface energy. High-energy UV radiation was found to play only a minor role in the surface modification of PP. Of the narrow range of ozone concentrations studied, no clear relationship was found to exist between ozone concentration and rate of modification of the surface; thus, the concentration of ozone must not affect the relative concentrations of products from the competing reactions. Increased surface oxidation and decreased contact angles were observed when the lamp-to-sample distance was minimized. The presence of water vapor during UVO treatment was found to lead to greater oxygen uptake after short-term treatments but did not result in increased surface energy. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2489–2501, 1999
TL;DR: In this paper, the side chains of poly(m-phenylene 4,4′-oxydiphthalimide)s containing various side chains, such as 6-(4-biphenylmethoxy) hexyloxy group and 6-(phenylphenoxy)hexyloxy isomers, were synthesized, giving thin films of high quality.
Abstract: New poly(m-phenylene 4,4′-oxydiphthalimide)s containing various side chains, such as 6-(4-biphenylmethoxy)hexyloxy group and 6-(phenylphenoxy)hexyloxy isomers, were synthesized, giving thin films of a high quality. All the polyimides apparently were almost amorphous, but exhibited short-range ordering in some extent, depending on the side chains. By incorporating side chains, the thermal properties, including stability, thermal expansivity, and glass transition temperature, were generally degraded, whereas the optical and dielectric properties were improved. All the polyimides exhibited a good rubbing processability and excellent performance in the controlling of both the alignment and the pretilt of LC molecules in the LC cell. The pretilt angle of LC molecules was easily achieved in a wide-angle range of 8–27°, depending upon the rubbing density as well as the incorporated side chains. The pretilting of LC molecules was very sensitive to all the molecular parameters (namely, the flexibility of polymer chain backbone as well as the isomeric structure of biphenyl mesogen end group, spacer length, and spacer conformation in the side chain) in the polyimide, in addition to the rubbing process. In particular, the side chains, which are much shorter in length than the long alkyl side chains in the polyimides being used widely as LC alignment layers, were evident to involve effectively in the alignment of and the pretilt of LC molecules, which are highly desired in the LC display industry. This might mainly be attributed to a strong interaction between the biphenyl mesogen end group of the side chain and the LC molecule. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2909–2921, 1999
TL;DR: In this paper, the effects of comonomer and cosolvent ratios on microsphere formation and morphology were described, and the results showed that the effect of these ratios on the morphology of microspheres can be significant.
Abstract: Monodisperse poly(chloromethylstyrene-co-divinylbenzene-80) microspheres of 4–6-µm diameter were prepared by precipitation copolymerization in neat acetonitrile and in acetonitrile/toluene mixtures. These particles have clean surfaces due to the absence of any added stabilizer and up to 0.5 cm3/g pore volume, depending on the comonomer ratio and on the amount of toluene cosolvent. The effects of comonomer and cosolvent ratios on microsphere formation and morphology are described. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2295–2303, 1999