Showing papers in "Polymer Bulletin in 1998"
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TL;DR: In this paper, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that so-modified silicate layers were finely dispersed in these polymeric matrices.
Abstract: Nanoscale composites of a modified silicate with either high-density polyethylene (HDPE) or a nitrile copolymer have been examined. Hydrophilic silicate clay was intercalated by ion exchange reaction of alkylammonium ions. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that so-modified silicate layers were finely dispersed in these polymeric matrices. Instead of being individually dispersed, most layers were found in thin stacks comprising several swollen layers. Greater dispersion was found in the nitrile copolymer rather than in HDPE, suggesting differences in the degree of physical interaction with the modified clay. Lamellar crystals of HDPE formed parallel to the silicate layers.
222 citations
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TL;DR: In this paper, the structural affinity between styrene monomer and the organic group of org-MMT plays an important role in the structure and properties of hybrid materials, and the resulting materials showed an expansion of interlayer distance.
Abstract: Styrene monomer was mixed with quaternary ammonium montmorillonites(org-MMTs) and polymerized in the presence of radical initiator. The resulting materials showed an expansion of interlayer distance. These hybrid materials exhibited higher thermal stability compared with the virgin polystyrene(PS) or PS/pristine-MMT microcomposite. PS/Bz-MMT, containing benzyl-unit similar to styrene in org-MMT, exhibited higher decomposition temperature even for MMT loading as low as 0.3wt.% compared with other PS/org-MMT hybrids. It was found that the structural affinity between styrene monomer and the organic group of org-MMT plays an important role in the structure and the properties of hybrid materials.
184 citations
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TL;DR: In this article, a modified micro-emulsion polymerization was used to obtain number-average diameters of 33-46 nm with narrow polydispersity (Dv/Dn= 1.1) and polymer content of 6-24 wt% using low levels of surfactant (dodecyltrimethylammonium bromide, DTAB).
Abstract: Nanosize poly(methyl methacrylate) (PMMA) microlatexes with high PMMA/surfactant ratio have been successfully prepared by a modified microemulsion polymerization, i.e., continuous and slow addition of monomer (MMA) to the polymerizing MMA microemulsion with mild stirring. Number-average diameters of 33–46 nm with narrow polydispersity (Dv/Dn= 1.1) and polymer content of 6–24 wt% were achieved using low levels of surfactant (dodecyltrimethylammonium bromide, DTAB) — less than 1 wt% of the reaction mixture. Particle diameter depended on polymerization temperature, MMA content, and concentrations of initiator and surfactant. Larger particles wereformed when temperature was too high, initiator concentration was too high, or surfactant concentration was too low.
105 citations
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TL;DR: In this article, atom transfer radical polymerization (ATRP) was demonstrated to yield well-defined polyacrylates with halogen end groups, which were transformed to azide groups which were subsequently reduced into amino groups.
Abstract: Atom transfer radical polymerization (ATRP) was demonstrated to yield well-defined polyacrylates with halogen end groups. These halogen end groups were transformed to azide groups which were subsequently reduced into amino groups. The replacement of the halogen end groups by azide groups was obtained either by using sodium azide or by treatment with trimethylsilyl azide in the presence of both stoichiometric and catalytic amounts of tetrabutylammonium fluoride (TBAF). The azide end groups were reacted with triphenylphosphine in order to obtain iminophosphorane groups which were then hydrolyzed yielding amino terminated polyacrylates.
97 citations
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TL;DR: In this article, the thermal and viscoelastic properties of polypropylene (PP)/cellulose as well as PP/Xylan composites were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermoanalysis (DMTA).
Abstract: The thermal and viscoelastic properties of polypropylene (PP)/cellulose as well as PP/Xylan composites were investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermoanalysis (DMTA). Morphological aspects were available by using polarizing light microscopy and scanning electron microscopy (SEM). Three types of fillers were incorporated in PP: xylan fillers (XL), cellulose microfibers (CM) and short fibers of spun cellulose (CS). The compatibilizer maleic anhydride modified PP (MAPP) was added to the composites. The crystallization temperature and crystallinity of PP apparently increased in the presence of all fiber types. The cellulose fiber surfaces act as nucleating agents for PP, resulting in the formation of transcrystalline regions around the fibers. The DMTA spectra of PP/filler composites revealed a significant increase in the stiffness and a remarkable decrease of the damping values. This effect was stronger for PP/CS than for the other composites. The results verify that improved compatibility and interfacial adhesion between fiber and matrix markedly contribute to an improvement of the mechanical properties.
88 citations
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TL;DR: By chain extending with a longer urethane diol block, a processible polymer was obtained with mechanical properties comparable to the polyurethane urea and has been made porous and can be used as a meniscal prosthesis.
Abstract: New biomedical polyurethanes and a polyurethane urea based on epsilon-caprolactone and 1,4-butanediisocyanate have been developed. On degradation, only non-toxic products are produced. The polyurethane urea with poly(epsilon-caprolactone) soft segments and butanediisocyanate/butanediamine hard segments shows a high tensile strength, a high modulus and a high resistance to tearing but as a result of the strong interactions between the solvent and the polymer processing is difficult. When butanediamine is replaced by butanediol in the chain extension step, a processible polyurethane is obtained but the polymer lacks the desired mechanical properties for biomedical applications. By chain extending with a longer urethane diol block, a processible polymer was obtained with mechanical properties comparable to the polyurethane urea. This polyurethane has been made porous and can be used as a meniscal prosthesis.
79 citations
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TL;DR: In this article, a novel morphology for linear ABC-triblock copolymers is presented, where A forms spherical microdomains, covered by small B-spheres and C forming the matrix.
Abstract: A novel morphology for linear ABC-triblock copolymers is presented, where A forms spherical microdomains, covered by small B-spheres and C forming the matrix This morphology is characterized by transmission electron microscopy and small angle X-ray scattering The morphology forms both in solution cast and melt extruded samples Qualitative arguments to understand the thermodynamic stability of this morphology are given
72 citations
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TL;DR: In this paper, the authors compared metallocene/methylaluminoxane and single component Pd(II)-catalysts for the vinyl polymerisation of norbornene.
Abstract: Metallocene/methylaluminoxane and single component Pd(II)-catalysts are compared to methylaluminoxane activated Ni and Pd-catalysts for the vinylpolymerisation of norbornene. Ni(II), Ni(0) and Pd(II)-compounds were found to be orders of magnitude more active than metallocenes and produce polymers of much higher molecular weights. Polymerisation kinetics for these systems have been studied in detail and reflected high initial activity followed by significant catalyst deactivation. Based on NMR-spectroscopy and WAXS five types of polynorbornenes have been identified and structures are proposed.
70 citations
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TL;DR: In this article, the authors investigated the effects of the PU content and its crosslink density on the mechanical properties and the toughness of PU/PLA blends, and showed that a proper amount of PU and a proper extent of cross-link cross-linking can achieve a higher hardness than pure PLA.
Abstract: Brittle polylactide (PLA) was toughened by introducing 5 wt % of a poly(ɛ-caprolactone)(PCL) diol- and triol-based polyurethane (PU) network. The extent of cross-linking of the PU was varied by changing the ratio between diol and triol. The effects of the PU content and its crosslink density on the mechanical properties and the toughness of PU/PLA blends were investigated. Maximum toughness of PU/PLA blends, an order of magnitute higher than that of pure PLA, could be achieved by the use of a proper amount of PU and a proper extent of cross-linking.
70 citations
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TL;DR: In this paper, molecularly imprinted polymeric membranes were prepared from carboxylated polysulfone, and the amino acid preferentially adsorbed by the membrane was also selectively permeated by electrodialysis.
Abstract: Molecularly imprinted polymeric membranes were prepared from carboxylated polysulfone. Membranes imprinted by Z-D-Glu recognize the D-isomer in preference to the corresponding L-isomer, and vice versa. The amino acid preferentially adsorbed by the membrane was also selectively permeated by electrodialysis.
66 citations
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TL;DR: Poly(α-t-butoxy-ω-styrylo-ethoxy ethyl glycidyl ether) was synthesized via the termination of the potassium t-butoxide initiated anionic polymerization of ethoxy-ethyl gly glycidyl (EGD) with p-chloromethylstyrene as mentioned in this paper.
Abstract: Poly(α-t-butoxy-ω-styrylo-ethoxy ethyl glycidyl ether) was synthesized via the termination of the potassium t-butoxide initiated anionic polymerization of ethoxy ethyl glycidyl ether with p-chloromethylstyrene. The macromonomer was copolymerized with styrene. Subsequent hydrolysis of the copolymers leads to polystyrene - graft - polyglycidol. Poly(α-t-butoxy-ω-styrylo-glycidol), synthesized through the hydrolysis of the macromonomer so obtained, acts as reactive emulsifier (surfmer) in the emulsion copolymerization of styrene in water.
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TL;DR: The influence of radiation dose and feed composition on the swelling properties, diffusional behavior of water and diffusion coefficients of the hydrogel systems were examined in this article, where N-vinyl-2-pyrrolidone/acrylonitrile hydrogels were used for adsorption of some water soluble dye such as basic blue 9, tetraethyl rhodamine, xylidine ponceau 2R, indigo carmine, helianthin and erythrosine.
Abstract: Swollen hydrogels were prepared by γ-radiation copolymerization of N-vinyl-2-pyrrolidone and acrylonitrile. The influence of radiation dose and feed composition on the swelling properties, diffusional behavior of water and diffusion coefficients of the hydrogel systems were examined. N-vinyl-2-pyrrolidone/acrylonitrile hydrogels were swollen in the range 50–850%. Water diffusion to the hydrogels generally was a non-Fickian type diffusion. The hydrogel were used in the studies of adsorption of some water soluble dye such as basic blue 9, tetraethyl rhodamine, xylidine ponceau 2R, indigo carmine, helianthin and erythrosine, and of a vitamin riboflavin (Vitamin B2).
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TL;DR: In this article, the authors describe the synthesis and characterization of amphiphilic triarm star block copolymers based on polystyrene, poly(methyl methacrylate), poly(e caprolactone), poly (l lactide) and poly(ethylene oxide) blocks.
Abstract: We describe the synthesis and the characterization of amphiphilic triarm star block copolymers based on polystyrene, poly(methyl methacrylate), poly(e caprolactone), poly(l lactide) and poly(ethylene oxide) blocks. This synthesis has been achieved by a new route consisting in 2 successive initiation steps on a core molecule (a 1,1-diphenyl-ethylene derivative bearing a protected hydroxy function) located at the end of a first block. Some results on adsorption onto TiO2 and micellization studies are given. Preliminary results on solid state indicate an increase of the miscibility of the different incompatible blocks.
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TL;DR: In this paper, the phase inversion process was investigated from different points of view, and a reliable on-line and off-line method of morphology detection using light microscopy was established.
Abstract: The phase inversion process was investigated from different points of view. First, a reliable on-line and off-line method of morphology detection using light microscopy is established. The method provides fast information that can be used to discriminate between different types of morphologies. Second, TEM images are modelled with Markov Random Fields. For characterization purposes image features are introduced and tested. A combination of features allows classification of different morphologies of PMMA/PS blends. In the third part we show that the rheological properties of blends allow also discrimination between different morphologies.
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TL;DR: Aryl phosphinate epoxy ether (DHQEPE) was synthesized in this paper, which is an effective flame retardant and thermal stabilizer for epoxy resins.
Abstract: A novel aryl phosphinate epoxy ether, 10-(2',5'-bis(glycidyloxy)phenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DHQEP), was synthesized. The structures of the obtained compounds were confirmed by mass, FTIR, 1H, 13C, 31P-NMR spectroscopies, elemental analysis, and X-ray single crystal analysis. In addition, compositions of DHQEP with common curing agents, e.g., 4,4'-diaminodiphenylmethane (DDM), 4,4'-diaminodiphenyl sulfone (DDS), and dicyanodiamide (DICY), were studied to compare their thermal and flame resistance with that of commercial epoxy resins. The aryl phosphinate epoxy-resin composites exhibited excellent thermal properties and a quite high limiting oxygen index (LOI) value as well as high char yield. Aryl phosphinate epoxy ether is shown to be an effective flame retardant and thermal stabilizer for epoxy resins.
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TL;DR: In this article, the application of copolymeric poly(acrylamide/ crotonic acid) (AAm/CA) hydrogels to agrochemicals (sodium 2,2 dichloropropionate (dalapon), ammonium nitrate, potassium nitrate and ammonium sulfate) was investigated.
Abstract: Summary The aim of this work was to test the application of new copolymeric poly(acrylamide/ crotonic acid) (AAm/CA) hydrogels to agrochemicals (sodium 2,2 dichloropropionate (dalapon), ammonium nitrate, potassium nitrate and ammonium sulfate) releases AAm/CA hydrogels containing agrochemicals is prepared by two different compos ition of crotonic acid and two different γ-rays doses The herbiside such as sodium 2,2 dichloropropionate (dalapon) and fertilizers such as ammonium nitrate, potassium nitrate and ammonium sulfate were trapped in the gels by including it in the feed mixture of radiation polymerization The equilibrium swelling degree in water was between 1020% and 1840% The swelling kinetics of the hydrogels were studied at 25 °C, and the initial swelling rate, swelling rate constant, maximum swelling, diffusional exponent and diffusion coefficient of the process were obtained The concentration of the released of agrochemicals from the hydrogels was determined by conductivity measurements The initial releasing rate, release rate constant, maximum concentration of releasing agrochemicals were calculated As a result, if AAm/CA hydrogels containing agrochemicals were swelled in water, release of agrochemicals was increased with the raising of crotonic acid quantities in the hydrogel and γ-rays doses
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TL;DR: In this paper, atomic force microscopy (AFM) was used to study the lamellar thickness and its distribution in the β modification of isotactic polypropylene-(β-iPP) crystallized from the melt at high temperatures.
Abstract: Atomic force microscopy (AFM) was used to study the lamellar thickness and its distribution in the β modification of isotactic polypropylene-(β-iPP) crystallized from the melt at high temperatures. Measurements were performed on lamellae oriented both flat-on and edge-on with respect to the examined surface. Average lamellar thickness was found to be dependent not only on the crystallization temperature, but also on factors such as nucleation density and isothermal lamellar thickening. The limitations and advantages of the AFM technique for evaluation of lamellar thickness are discussed.
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TL;DR: In this paper, it was shown that the melting of flexible macromolecules in an irreversible process is due to an inherent annealing process, and that the reversing heat capacity that characterizes this effect decreases with time.
Abstract: Although melting of flexible macromolecules in an irreversible process, it was demonstrated recently with temperature-modulated calorimetry (TMC) that some of the overall melting may be reversible within a fraction of a kelvin. This was taken as evidence for incompletely melted molecules with a remaining molecular nucleus. The reversing heat capacity that characterizes this effect was observed to decrease with time. It is shown by new TMC experiments that this time effect is not induced by the temperature modulation, but is due to an inherent annealing process. It is also proven that it is not dependent on the type of calorimeter.
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TL;DR: In this article, 2-furfurylmaleimide (FM) was synthesized and characterized unambiguously for the first time by condensing FM with maleic anhydride to give the corresponding maleamic acid which was in turn cyclized in the presence of acetic anhydrides and sodium acetate.
Abstract: 2-furfurylmaleimide (FM) was synthesized and characterized unambiguously for the first time by condensing 2-furfurylamine with maleic anhydride to give the corresponding maleamic acid which was in turn cyclized in the presence of acetic anhydride and sodium acetate. A thorough structural assessment was carried out to prove the success of this procedure. FM is highly sensitive to ring-opening hydrolysis by atmospheric moisture and must be kept in a dry medium. This investigation was aimed at using FM as an AB-type monomer in a polycondensation based on the Diels-Alder reaction. Preliminary experiments are reported on this novel system which provided the first polycondensates of this kind.
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TL;DR: Palladium (II) compounds (palladium dichloride, acetate and acetylacetonate) in conjunction with triphenylphosphine dissolved in 1-butyl-methyl imidazolium tetrafluoroborate, hexafluorophosphate or trifluoromethanesulfonate are able to dimerize butadiene into 1,3,6-octatriene in a typical two-phase catalytic reaction with 100% selectivity as mentioned in this paper.
Abstract: Palladium (II) compounds (palladium dichloride, acetate and acetylacetonate) in conjunction with triphenylphosphine dissolved in 1-butyl-methyl imidazolium tetrafluoroborate, hexafluorophosphate or trifluoromethanesulfonate are able to dimerize butadiene into 1,3,6-octatriene in a typical two-phase catalytic reaction with 100% selectivity. The reaction product is easily separated from the reaction mixture by simple decantation, and the recovered ionic liquid catalyst solution can be reused several times without significant changes in catalytic activity or selectivity.
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TL;DR: In this paper, a polyurethane based on a 50/50 copoly(L-lactide/epsilon-caprolactone) prepolymer and butanediisocyanate was made.
Abstract: Polyurethanes based on a 50/50 copoly(L-lactide/epsilon-caprolactone) prepolymer and butanediisocyanate were made. Chain extending a diisocyanate terminated prepolymer with butanediamine was not possible due to the susceptibility of the lactide bond to aminolysis. Chain extension with butanediol resulted in a polymer with poor mechanical properties due to transesterification. When the copolymer prepolymer was chain-extended with an isocyanate terminated block, transesterification with the chain-extender was avoided and the mechanical properties were increased. When the length of the hard segments was increased the mechanical properties increased further. A L-lactide/epsilon-caprolactone based polyurethane with a tensile strength and modulus of respectively 45 MPa and 60 MPa was made. The polymer contained no poly(L-lactide) crystals and was easy to process. Compared to the high molecular weight 50/50 copoly(L-lactide/epsilon-caprolactone) the polyurethane showed better mechanical properties, is expected to have the same adhesive properties and is expected to have a slower degradation rate. These factors makes this polymer excessively useful for in-vivo tissue engineering in for instance meniscal reconstruction material, nerve guide and artificial skin.
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TL;DR: In this article, the in-situ monitoring of the living carbocationic polymerization of isobutylene (IB) and styrene (St) with a fiber optic ATR probe in the mid-IR "fingerprint" range is reported.
Abstract: The in-situ monitoring of the living carbocationic polymerization of isobutylene (IB) and styrene (St) with a fiber optic Attenuated Total Reflection (ATR) probe in the mid-IR "fingerprint" range is reported here for the first time. Monomer consumption was followed by the disappearance of the C=C stretching for both IB and St, and the C−H bending of the CH3-group in IB. The formation of polyisobutylene (PIB) was also monitored by tracing the asymmetrical doublet characteristic of C−H bending of the t-butyl groups of the PIB. Conversion measurements by conventional off-line gravimetry correlated well with the new technique.
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TL;DR: In this paper, the diblock copolymer of methyl methacrylate and 1H,1H, 2H,2H-perfluorooctyl methacylate was shown to form micelles which could be deposited and imaged on a flat substrate upon casting from a solvent which is selective for the PMMA block, e.g. toluene and THF.
Abstract: The diblock copolymer of methyl methacrylate and 1H,1H,2H,2H-perfluorooctyl methacrylate was shown to form micelles which could be deposited and imaged on a flat substrate upon casting from a solvent which is selective for the PMMA block, e.g. toluene and THF. The micelle formation was significantly affected by a small content of PMMA homopolymer. While the pure blockcopolymer formed cylindrical micelles, the presence of the PMMA shifted the associated equilibrium to the side of spherical aggregates.
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TL;DR: The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy.
Abstract: The melting and crystallization behavior of poly(β-hydroxybutyrate) (PHB) and poly(ethylene succinate) blends has been studied by differential scanning calorimetry and optical microscopy. The results indicate that PHB and PES are miscible in the melt. Consequently the blend exhibits a depression of the melting temperature of both PHB and PES. In addition, a depression of the equilibrium melting temperature of PHB is observed. The Flory-Huggins interaction parameter (X 12 ), obtained from melting point depression data, is composition dependent, and its value is always negative. Isothermal crystallization in the miscible blend system PES/PHB is examined by polarized optical microscope. The presence of the PES component gives a wide variety of morphologies. The spherulites exhibit a banded structure and the band spacing decreases with increase PES content.
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TL;DR: In this paper, the authors studied the thermal stabilities of α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers and showed that the loss of functional end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen.
Abstract: Thermal stabilities of α,ω-hydroxypropyl, α,ω-hydroxybutyl, α,ω-2-hydroxypentyl and α,ω-hydroxyhexyl terminated polydimethylsiloxane (PDMS) oligomers were studied. Hydroxypropyl and hydroxybutyl terminated polydimethylsiloxane oligomers showed degradation upon heating, through the loss of functional end groups as determined by FT-IR spectroscopy and gel permeation chromatography. α,ω-Hydroxyhexyl and α,ω-2-hydroxypentyl terminated polydimethylsiloxane oligomers were stable under similar conditions. Instability of the end groups is due to the back biting of the terminal silicon in the PDMS by the primary hydroxyl oxygen, leading to the formation of 5 and 6 membered, stable, heterocylic compounds. Loss of end groups also resulted in a dramatic increase in the molecular weights of the oligomers produced, as determined by gel permeation chromatography.
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TL;DR: In this paper, the relative contrast in height and phase mode images of the phase separated regions was found to be very sensitive to changes in the operating conditions of the microscope and was observed for the tri-block copolymer system examined in this study.
Abstract: Thin films of phase separated polystyrene-b-polyisoprene-b-polystyrene block copolymers were studied by tapping mode atomic force microscopy. The relative contrast in height and phase mode images of the phase separated regions was found to be very sensitive to changes in the operating conditions of the microscope. Contrast variations and reversals were observed for height and phase mode images as a function of the set-point amplitude ratio and drive frequency. No unique height or phase contrast was observed for the the tri-block copolymer system examined in this study.
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TL;DR: In this paper, the effects of temperature and IB/isoprene feed ratio on copolymer molecular weights were determined and compared with those produced by AlCl3 in the presence of CH33Si[B(C6F5)4] initiating system.
Abstract: As a sequel to our studies on isobutylene (IB) homopolymerizations, we have investigated the copolymerization of IB/isoprene (IP) mixtures containing up to ∼20 mole% IP in the feed by the use of the in situ (CH3)3Si[B(C6F5)4] initiating system in close-to-neat monomers in the temperature range from −35 to −8 (reflux)°C. The effects of temperature and IB/IP feed ratio on copolymer molecular weights were determined and compared with those produced by AlCl3. The molecular weights of butyl rubbers obtained by the novel initiating system under a variety of conditions are invariably and significantly higher than those made with AlCl3. High molecular weight gel-free rubbers containing up to ∼5 mol% unsaturation can be obtained at relatively high temperatures. Copolymer compositions can be controlled by the IB/IP ratio in the feed. Product molecular weights decrease with increasing IP content. To gain insight into the copolymerization mechanism, the activation enthalpy of molecular weights (ΔH‡=−5.9 kcal/mol, −24.7 kJ/mol) and the reactivity ratios (rIB= 1.8, rIP= 1.5) have been determined.
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TL;DR: In this paper, a block copolymer with short and long polytetrahydrofuran segments was obtained by potentiostatic anodic polymerization of pyrrole in different electrolytic media.
Abstract: Bifunctional living polytetrahydrofuran (PTHF) was terminated with potassium salt of pyrrole to yield polymers with electrochemically active end groups. These polymers were employed in the second stage to obtain conducting polypyrrole/polytetrahydrofuran block copolymers with short and long polytetrahydrofuran segments by potentiostatic anodic polymerization of pyrrole in different electrolytic media. Syntheses of block copolymers were achieved in media where tetrabutylammonium fluoroborate, sodium perchlorate and sodium p-toluenesulfonate were used as the supporting electrolytes. Characterizations were based on DSC, TGA, SEM, FTIR, and CV analyses. No significant effect of the chain length of polytetrahydrofuran segments on the properties of the copolymers was observed; however, thermal, electrochemical behaviors, and surface morphologies of the films were greatly affected by the supporting electrolytes.
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TL;DR: In this article, two couples of phenanthrene and anthracene labelled copolymers are used to prepare micellar solutions by mixing them before and after dialysis. But the non radiative energy transfer is determined on these solutions to prove that polystyrene-poly(ethylene oxide) diblock copolymer micelles in water are "frozen" micells even when heated near the Tg of poly styrene.
Abstract: Micellization in water of polystyrene–poly(ethylene oxide) diblock copolymers is achieved by the stepwise dialysis technique in order to prepare micellar solutions for copolymers with a wide range of molecular parameters. Hydrodynamic radii, determined by quasielastic light scattering, are correlated with the molecular parameters, e.g. molecular weight and composition, and compared with the theory. Two couples of phenanthrene and anthracene labelled copolymers are used to prepare micellar solutions by mixing them before and after dialysis. The non radiative energy transfer is determined on these solutions to prove that polystyrene-poly(ethylene oxide) diblock copolymers micelles in water are "frozen" micelles even when heated near the Tg of polystyrene.
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TL;DR: In this article, pyromellitic dianhydrides with side chains were synthesized and polymerized with 4,4'-oxydianiline (ODA) in NMP at room temperature.
Abstract: New pyromellitic dianhydrides having (n-alkyloxy)phenyloxy (-O-Ph-O-n-CmH2m+1, m=1,4,8,12) side chains were synthesized and polymerized with 4,4'-oxydianiline (ODA) in NMP at room temperature. Imidization was carried out using triethylamine and acetic anhydride. The synthesized polyimides (Cm-OPIs) were characterized and their properties were measured and discussed in respect to the effects of side chains. Inherent viscosities of the polymers were in the 0.46 – 0.68 dL/g range. All the polymers were highly soluble in N-methylpyrrolidinone (NMP) and slightly soluble in DMSO, m-cresol, DMF and concentrated H2SO4 at room temperature. TGA pyrograms showed two-step degradation. In DSC thermograms the polymers exhibited Tg's between 219°C and 305°C and melting points near 350°C were observed in C8- and C12-OPIs. Wide-angle X-ray diffractometry for as-polymerized samples revealed very low crystallinities and layered structures which were better developed in the polymers with longer side chains.