Showing papers in "Journal of Polymer Science Part A in 1974"

Simultaneous polymerization and formation of polyacetylene film on the surface of concentrated soluble Ziegler-type catalyst solution

Abstract: A direct method of simultaneously polymerizing and forming acetylene monomer to produce uniformly thin films of polyacetylene was investigated in terms of catalyst system, catalyst concentration, and polymerization temperature. The best catalyst was a Ti(OC4H9)4–Al(C2H5)3 system (Al/Ti = 3–4) and the critical concentration was 3 mmole/l. of Ti(OC4H9)4. Below the critical concentration, only a solid or a powder was obtained. The configuration of the polymers obtained depends strongly upon the polymerization temperature. Thus an all-cis polymer was obtained at temperatures lower than −78°C, whereas an all-trans polymer resulted at temperatures higher than 150°C. Observations either in an electron microscope by direct transmission or in a scanning electron microscope showed that the film is composed of an accumulation of fibrils about 200–300 A in width and of indefinite length.

Studies on the photooxidation mechanism of polymers. I. Photolysis and photooxidation of polystyrene

Abstract: A new mechanism has been proposed for the photooxidation of polystyrene as film and in benzene. The initial stage of the photooxidative degradation may involve reactions of singlet oxygen with polystyrene molecules. Singlet oxygen may be formed in the reaction between excited benzene ring in polystyrene molecule and molecular oxygen. The addition of singlet oxygen quenchers such as 1,3-cyclohexadiene or β-carotene reduces the rate of polymer degradation in benzene solution. The mechanisms of the photolysis of polystyrene as film and in benzene solution, in vacuo and in the presence of oxygen, are discussed and interpretations proposed. The pronounced yellowing of polystyrene during the photooxidation process is interpreted as a reaction involving benzene ring-opening photooxidation in polystyrene molecule. These results were obtained by comparing ultraviolet and infrared spectra in experiments of photooxidation of pure liquid benzene and polystyrene film.

Gel-permeation chromatography: X. Molecular weight detection by low-angle laser light scattering

Abstract: Effluent from a gel-permeation chromatographic column has been simultaneously and continuously monitored with a differential refractometer and a low-angle laser light-scattering (LALLS) photometer. This provides a true and direct determination of molecular weight distribution rather than through a calibration method as obtained by conventional GPC techniques. Computer assisted data reduction provides a rapid determination of Mw, Mn, Mz, Mw/Mn, as well as a plot of molecular weight distribution. Samples of very narrow molecular weight distribution (MWD) polystyrene from Pressure Chemicals Co. and relatively wide MWD samples of poly(methyl methacrylate) in chloroform have been characterized.

Phenolic resins for solid‐phase peptide synthesis: Copolymerization of styrene and p‐acetoxystyrene

Abstract: Details are given of the synthesis and purification of p-acetoxystyrene and its solution and suspension copolymerization with styrene. Reactivity ratios, evaluated by the Tidwell-Mortimer method, were r1 (p-acetoxystyrene) = 1.18, and r2 (styrene) = 0.88 for (bulk) solution copolymerization. Corresponding values of the reactivity ratios for suspension copolymerization were, within experimental error, indistinguishable from unity. Thus the copolymer composition is governed simply by the monomer feed composition. Use of a specially designed reactor vessel permits convenient suspension copolymerization of styrene, p-acetoxystyrene, and divinylbenzene to give crosslinked resins having comparatively narrow particle size distributions. Acetoxy groups in the crosslinked resin are cleaved by hydrazine hydrate under very mild conditions to give crosslinked polystyrenes having phenolic groups which, in turn, provide a useful alternative to the more usual chloromethylated polystyrene resins for solid-phase peptide synthesis.

Synthesis and characterization of polyaryloxyphosphazenes

Abstract: The synthesis, dilute solution characterization, and thermal analysis of seven polyaryloxyphosphazenes are described. Synthesis is accomplished by the ring-opening polymerization of hexachlorocyclotriphosphazene at 245°C, followed by reaction of polydichlorophosphazene with sodium aryloxide salts in solution at 115°C. Polymers prepared and characterized have the general structure [(ArO)2PN]n, with Ar = C6H5, m- and p-CH3C6H4, m- and p-ClC6H4, p-C2H5C6H4, or p-CH3OC6H4. Elemental and infrared analyses show these polymers are essentially free of reactive chlorine sites. All the polymers displayed high intrinsic viscosities [η] > 1 dl/g, in tetrahydrofuran or chloroform. Closer examination of the dilute solution properties of two polyaryloxyphosphazenes revealed high molecular weights (Mw> 6 × 105) and broad molecular weight distributions (Mw/Mn > 4.7). The experimental values for the Z-average radii of gyration, 〈S2〉z1/2, characterized at near theta conditions, are larger than the calculated values for a freely rotating chain, which suggests that these polymers are relatively linear and not highly branched. Thermal analysis revealed second-order glass transitions between −37 and +13°C and first-order endothermic transitions between 43 and 160°C for the different polymers. Although crystalline structure can persist above this first-order transition, this temperature can be regarded as a melting temperature or softening temperature at which films can be molded. Decomposition temperatures, measured in argon and oxygen, ranged from 250°C to 400°C.

Anionic polymerization initiators containing protected functional groups and functionally terminated diene polymers

Abstract: Organolithium reagents substituted with hydroxyl-carrying mixed acetals (i.e., tetra-hydropyranyl and α-ethoxyethyl ethers) have been prepared in high yields and used to polymerize 1,3-butadiene to various acetal-terminated polybutadiene polymers. A method is described for converting acetal-containing polymers into hydroxyl-containing polymers. The polybutadienes have been characterized with regard to endgroup types, quantitative functionalities, molecular weights, molecular weight distributions, and microstructures. Dihydroxyl terminated polymers are prepared anionically in the absence of gel. Such materials are more suitable from the standpoint of f(OH) and Mw/Mn for chain extension studies than are prepolymers prepared by radical methods.

Free-radical grafting of monomers to polydienes. II. Kinetics and mechanism of styrene grafting to polybutadiene

Abstract: A kinetic analysis of the grafting reaction has shown that, provided rubber radicals are not involved in termination reactions, the observed normal kinetics of styrene polymerization are to be expected. An expression relating the graft fraction with the rubber and monomer concentrations has been derived and its validity verified from the results reported in Part I. The observation that the molecular weight of the ungrafted PBD falls during the reaction has been explained on a theoretical basis.

Reaction of poly(vinyl alcohol) with potassium persulfate and graft copolymerization

Abstract: A study of the oxidation of poly(vinyl alcohol) (PVAL) by potassium persulfate (KPS) in aqueous solutions showed that the decomposition of KPS was greatly enhanced by the presence of PVAL, its hydroxyl groups being oxidized to ketones in a yield of about one mole of ketone from one mole of KPS. The decomposition rate of KPS was found to be given by the equation, −d[S2O82−]/dt = k[S2O82−] [PVAL]1/2, which was essentially the same as in the oxidation of alcohols of low molecular weight by persulfate ion. The occurrence of gelation of PVAL solutions and graft copolymerization of methyl methacrylate (MMA) onto PVAL in the presence of KPS was evidence for PVAL radical as an intermediate species in the oxidation of PVAL. A characterization study was also carried out for the reaction products of the graft copolymerization of MMA onto PVAL with KPS in dimethyl sulfoxide solution.

Polymerization of acetylenes catalyzed by arene–group vib tricarbonyls

Abstract: The polymerization of phenylacetylene and other terminal and internal alkynes has been achieved in homogeneous reactions catalyzed by ArM(CO)3, where Ar is an arene; M is Cr, Mo, or W. The polymerization of phenylacetylene proceeds by way of an intermediate which has been isolated and identified as a ladder compound composed of fused cyclobutane rings. The ladder compound, which is stable in the absence of the catalyst, breaks down in the presence of the catalyst to give the final polyconjugated polymer. Available evidence indicates that the conversion of the ladder compound to polyphenylacetylene proceeds by way of a free-radical mechanism. A mechanism for the electronic conversion of the ladder compound to the final polymer is proposed, as is a method of chain propagation.

Epoxy/modifier block copolymers

Abstract: The curing of epoxy resins with anhydrides in the presence of dihydroxyl-terminated polyester or polyether modifiers produces block copolymer structures in which one “block” is the crosslinked epoxy/anhydride network and the other block is the linear modifier segment. The morphology of the cured system is dependent upon modifier molecular weight. The critical molecular weight of polycaprolactone and poly(propylene oxide) is 3000–5000. Below this level, single morphological phase systems are obtained, but two-microphase systems result above this level. This behavior is displayed by several epoxy resins. Two-phase systems display a superior balance of heat distortion temperature and impact strength, thus providing tough systems with greater elevated temperature capabilities than are obtained with single-phase systems.

Pyrolysis of poly(vinyl chloride)

Abstract: A pyrolysis–gas chromatography–mass spectrometric technique has been developed to study the thermal degradation of poly(vinyl chlorides) polymerized at different temperatures. Hydrogen chloride and benzene evolution during successive stages of pyrolysis have been quantitatively determined and correlated to the tacticity and molecular weight of the polymer. It was found that lowering the temperature of polymerization and molecular weight depresses benzene evolution and increases char weight but does not affect the HCl yield. It is suggested that the syndiotactic trans microstructure favored at low temperature of polymerization yields polyenes which cannot cyclize to form benzene. As the molecular weight decreases, the increase in number of vinyl chain ends facilitates pyrolytic crosslinking and char formation.

Imidization during polymerization of acrylamide

Abstract: The spontaneous imidization of acrylamide during polymerization has been studied in three media: benzene, diglyme, and water. The data indicate that neither medium, time, nor temperatures below 140°C cause imidization to occur. The ascription of the low nitrogen found in polyacrylamide by some investigators to imide formation appears to be in error. The low nitrogen is due rather to retained solvent and/or water, for which polyacrylamide has a strong affinity. Imidization may be brought about by strong acids. The solubility of an imidized polyacrylamide decreases with increasing imide content.

Cyclopolymerization. II. Mechanism of the free-radical polymerization of N-n-propyldimethacrylamide

Abstract: The mechanism of cyclopolymerization was investigated by using N-n-propyldimethacrylamide (PDMA). Completely cyclized polymers were formed on polymerization of PDMA by a radical initiator. Moreover, those copolymers of PDMA and various monomers, such as styrene, methyl methacrylate, and vinyl acetate, obtained did not contain any detectable pendent double bonds. The kinetic investigation showed that the termination reaction proceeded between the cyclized radicals. The attempted polymerization of N-n-propyl-N-isobutyrylmethacrylamide, the monofunctional counterpart of PDMA, was failed. These results appear to confirm that cyclopolymerization of PDMA proceeds through a concerted mechanism which has been proposed for the mechanism of the cyclopolymerization of various difunctional monomers. Measurement of the ESR spectra of propagating radical has, however, revealed that the rate-determining step of the cyclopolymerization of PDMA is not intermolecular propagation but intramolecular cyclization, which indicates that the cyclization reaction proceeds in a stepwise way. This apparent contradiction was explained based upon thermodynamic considerations.

Photostabilization of polypropylene. II. Stabilizers and hydroperoxides

Abstract: The effects of various polyolefin photostabilizers on the thermal and photodecomposition of model and polymeric hydroperoxides have been investigated, both in the liquid and solid phases. Several extremely effective ultraviolet stabilizers belonging to the metal chelate class can cause the rapid thermal decomposition of model and polymeric hydroperoxides. Although stabilizers did not reduce the quantum yield for polypropylene hydroperoxide photolysis, several additives can scavenge hydroxyl and macroalkoxy radical products which result from hydroperoxide photolytic cleavage. Ultraviolet stabilizers which were found to trap radicals were able to prevent the photodegradation of polypropylene which already contained a significant concentration of hydroperoxide groups. Highly effective polypropylene ultraviolet stabilizers probably operate by a range of mechanisms including hydroperoxide decomposition, radical scavenging and singlet oxygen quenching.

Synthesis of polymers by using divalent metal salts of mono(hydroxyethyl) phthalate: Metal‐containing polyurethanes

Abstract: A series of metal-containing polyurethane-ureas containing ionic links in the main chain was synthesized by the polyaddition reaction of hexamethylene diisocyanate with mixtures of metal salts of mono(hydroxyethyl) phthalate and bisureas containing two hydroxyl groups which were obtained from monoethanolamine and diisocyanates. The polyurethane-ureas obtained were generally yellowish powders or solids. Close agreement between observed and calculated values of metal content of the metal-containing polyurethane-ureas was obtained. The viscosities (in dimethylformamide) of polyurethane-ureas decreased markedly with increase of metal content. Moreover, the decomposition temperatures were lowered a little by introducing metals into the polyurethane-ureas. Dimethylformamide, m-cresol, and dimethyl sulfoxide were comparatively good solvents for the metal-containing polyurethane-ureas; however, the polymers were insoluble in all other solvents.

Diffusion into and adsorption of polyethylenimine on porous silica gel

Abstract: The polyethyleneimine (PEI)–water–silica gel absorption system was used as a model system to investigate the relationship between diffusion into the porous structure, adsorption rate, and molecular weight of the polymer. Three silica gels, Porasil A, B, and and C having a range of characteristic porosity were used as adsorbents. Adsorption of PEI on Porasil C, which has the majority of its pores much larger than the dimensions of the adsorbate molecule, increased initially with increased molecular weight but became nearly constant at higher molecular weight. Little increase in adsorption occurred for this silica gel with increased ionic strength or with increased pH between 9.5 and 10.8. In contrast, adsorption increased sharply with increased ionic strength and for the same pH range on Porasil A. Molecular weight dependence was reversed. Adsorption decreased with increased molecular weight on Porasil A. In this case, the molecular size of PEI investigated was the same as the majority of pore apertures in the adsorbent. Solution environments (i.e., pH and ionic strength) that decrease the size of the PEI molecule and its affinity for the anionic silica gel surface, thus enabling it to more readily diffuse into the smaller porous regions of the adsorbent, are the apparent causes of the very large adsorption increase. Electrostatic repulsion between PEI molecules do not appear greatly to affect adsorption. Similar adsorption behavior has been reported in the literature for the PEI–cellulosic fiber adsorption system. Maximum adsorption on Porasil A occurred at pH 10.8, the same maximum generally reported for adsorption of PEI on cellulosic fibers. In this case, the silica gel (Porasil A) was found to have a pore size distribution and specific surface area of the same magnitude as cellulosic fibers prepared in the expanded state.

Crystallization-induced reactions of copolymers. IV. Ester-interchange reorganization of poly(ethylene terephthalate-co-2-methylsuccinate)

Abstract: The application of ester-interchange reactions to the crystallization-induced reorganization of random to block copolymers, which was demonstrated in the previous paper of this series, was followed quantitatively in this investigation. Structural changes based upon dyad compositions in copolyesters of terephthalic acid and 2-methylsuccinic acid with ethylene glycol were determined by high-resolution NMR. Sequence length distributions so calculated were related to the effects of copolymer composition, catalyst concentration, and reaction temperature on the rate of the ordering process and to the effect of structure on crystalline properties.

Aromatic polyethers, polysulfones, and polyketones as laminating resins. III

Abstract: 4,4′-Diphenoxydiphenylsulfone was polymerized with isophthaloyl chloride and terephthaloyl chloride in Friedel-Crafts polymerizations. These polymers had 5-cyanoisophthaloyl units in the backbone obtained either by using 1,3-bis(p-phenoxybenzoyl)-5-cyanobenzene or 5-cyanoisophthaloyl chloride as part of the acid chloride monomer. A terpolymer having 22 wt-% 5-cyanoisophthaloyl unit was also prepared from the Friedel-Crafts polymerization of 1,3-bis(p-phenoxybenzenesulfonyl)benzene and 5-cyanoisophthaloyl chloride. These terpolymers were crosslinked through heating to give insoluble products which proved to be thermally less stable than the uncrosslinked polymers.

Synthesis and some properties of poly-(2,5-trimethylene benzimidazole) and poly-(2,5-trimethylene benzimidazole hydrochloride)

Abstract: A polymer, poly(2,5-trimethylene benzimidazole), the first of a new family of nonsymmetrical polymers, was synthesized via an eight-step synthetic route. The polymer, obtained by melt polymerization, is amorphous and in its neutral form behaves as a moderate insulator. It forms 1 : 1 HCl adducts. When cast from formic acid solution, it forms 1 : 1 formic acid adducts. The acid adducts are semiconductors with resistivities in the 106–108 ohm-cm range. Space-charge effects are generated in the adducts as carrier mobility rises.

The macroester ⇄ macroion equilibrium in the cationic polymerization of THF observed directly by 300 MHz1 H NMR

Abstract: Two isomeric forms of active chain ends were observed simultaneously in the living cationic polymerization of tetrahydrofuran (THF) initiated with derivatives of trifluoromethanesulphonic acid (CF3SO2OH). These forms are the macroion and the macroester. Concentrations of both species were determined in the polymerization of THF conducted in CCl4, CH2Cl2, and CH3NO2, by using 300 MHz 1H NMR spectroscopy. In CCl4 the macroester form dominates (96%), and in CH3NO2 only 8% of macroester could be detected. In CH2Cl2 both species coexist in comparable concentrations ([macroion]:[macroester] = 1:3). The present direct measurements are in agreement with our previous determination of the proportions of macroester and macroions based on kinetics data. Therefore, this also confirms our earlier conclusion, that if an equilibrium between the macroions and macroester is involved in the polymerization of THF, the chain growth proceeds almost exclusively on the macroions.

Solid‐state polymerization of a cyclic diacetylene

Abstract: Large polymeric single crystals of a unique ring-bridged polymer have been produced by the solid-state polymerization of a cyclic diacetylene (o,o′-diacetylenyldiphenyl glutarate). These crystals are of high thermal stability, metallic in appearance with an asbestos-like texture, infusible, and insoluble. Single-crystal x-ray diffraction investigation indicates that the polymer is monoclinic (probable space group C2/c or Cc) with a unit cell containing four monomer units of dimensions α = 20.8 A, b = 8.0 A, c = 9.7 A, and β = 106°. Infrared spectra eliminate the previously suggested possibility that the solid-state reactivity of the above monomer corresponds to either reaction of the carbonyl function with the acetylenic bond or the cleavage of the ester linkage. Diffraction, dichroism, and Raman spectral studies indicate instead that the reaction proceeds by 1,4-addition polymerization at the diacetylene group to produce a trans–trans polymer of structure where the curved lines represent the di-(o-phenyl)-glutarate linkages which are on opposite sides of the chain for adjacent monomer units.

Photochromic behavior of copolymers of indolinospirobenzopyrane methacrylic derivatives

Abstract: Three photochromic 3,3-dimethyl-6′-nitroindolinospirobenzopyran methacrylic derivatives have been synthesized, namely, 1-methyl 8′-methacryloxymethyl (A), 1-(β-methacrylamidoethyl) (B), and 1-(β-methacryloxyethyl) (C). They have been copolymerized with methyl, isobutyl, and n-propyl methacrylates. The photochromic behavior of these copolymers in the solid state has been compared to that of the homologous isobutyric compounds dissolved in corresponding polymeric matrices. The kinetics of decoloration were resolved in three simultaneous first-order reactions with rate constants k1, k2, and k3. The influence of the polarity of the polymeric matrix and of the photochrome incorporation has been examined. The rates of decoloration of the copolymers with isobutyl and n-propyl methacrylate are very sensitive to the glass transition temperature Tg; the activation energy of decoloration increases markedly above Tg, from 19.8 to 36.5 kcal; below Tg the entropy of activation is strongly negative (around -20 e.u.), above Tg strongly positive. These effects are interpreted on the basis of an increasing chain segment mobility above Tg.