摘要:

Photoirradiations onto polycyclic acetals, i. e., polymers containing cyclic acetal groups in the molecule, were carried out at 30 or 40°C. The terpolymer of vinyl formal/vinyl acetate/vinyl alcohol (PVFAcA) was decomposed by means of irradiation, while poly-2-vinyl-1,3-dioxolane (PVDO) and poly-2-vinyl-4-hydroxy-methyl-1,3-dioxolane (PVHDO) were crosslinked. These results indicate the possibility of control of the decomposition or the crosslinking of polymer.

ISSN:0022-233X    

DOI:10.1080/00222338008056713

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Styrene (St) and methyl methacrylate (MMA) were photopolymerized in the presence of poly-2-vinyl-1,3-dioxolane (PVDO), poly-2-vinyl-4-hydroxymethyl-1,3-dioxolane (PVHDO), or the terpolymer of vinyl formal/vinyl acetate/vinyl alcohol (PVFAcA) at 30 or 40°C. The ability to accelerate the photopolymerization increased in the order PVFAcA < PVHDO < PVDO; the ability of pendent cyclic acetal was larger than that of cyclic acetals which are not pendent. Moreover, the promoting ability per cyclic acetal increased with the increase in the number of cyclic acetal cyclic acetal group in the molecule.

ISSN:0022-233X    

DOI:10.1080/00222338008056714

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A wide variety of polymers and copolymers of 1,3-dienes have been modified at low temperatures via the ene reaction with 4-substituted l,2,4-triazoline-3,5-diones. The resulting modified polymers were characterized via infrared spectroscopy, nuclear magnetic resonance, intrinsic viscosity, gel-permeation chromatography, differential scanning calorimetry, solubility tests, and tensile measurements. Physical properties measurements support the postulate that the highly polar pendant urazole groups contribute inter molecular and intramolecular hydrogen-bonding interactions and thus impart to the modified polymers thermoplastic elastomer properties. Changes in the solubility character, thermal behavior, and tensile properties of the modified polymers are in accord with this postulate. Since the association between molecules is physical in nature, the modified polymers remain soluble in appropriate solvents. They also show dramatic decreases in molecular size; for example, the average molecular size of polymers at 1% modification is about one tenth that of the unmodified polymer due to intramolecular interactions, a size reduction of the same order of magnitude as that of chemically crosslinked polymers. Poly-1,2-butadiene, when modified to the extent of 5%, gave values for elongation to break, Young's modulus, and tensile strength twice those for the parent polymer, while tensile recoveries were > 90%.

ISSN:0022-233X    

DOI:10.1080/00222338008056715

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Plasma polymerization of hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDSZ) monomers has been carried out in audio- (2 kHz, 20 kHz), radio- (5 MHz), but principally in microwave (2.45 GHz) frequency discharges. Film growth kinetics on glass and aluminum substrates have been studied by thickness and gravimetric measurements; the combined data have led to precise determinations of the film densities. The density data, in turn, provide strong evidence for a hitherto unreported structural feature, namely, that films are composed of a dense solid phase, and a thin (∼ 500 Å) “oligomeric” surface layer. The solid component is about 70% denser than the equivalent “conventional” polymer, and has a marked inorganic character, as revealed clearly by infrared spectroscopy. IR analyses of polymers produced in lower frequency discharges tend to show narrow, well resolved absorption bands. In the case of 2.45 GHz films, on the other hand, bands corresponding to “inorganic” linkages tend to become broader and more intense, and structural features become smeared-out. This is indicative of extensive crosslinking and of the inorganic structural content already mentioned. These results indicate intense fragmentation of monomer molecules in the microwave plasma, as also substantiated by pressure-rise measurements. Radical species created by abstraction of hydrogen, methyl, or other groups are responsible for film formation and growth and for crosslinking reactions within the film.

ISSN:0022-233X    

DOI:10.1080/00222338008056716

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The effect of counterion types on the structure of Cu(II) complexes of imidazole and poly-4(5)-vinylimidazole in aqueous solution was studied by spectroscopic and electron spin resonance (ESR) techniques. Visible and ESR spectra of both complexes in aqueous solution containing NaClO4, KNO3, KC1, and KBr showed only a slight change from each other in the presence of different counterions. On the other hand, the frequency of the center of absorption band in the visible region (λmax) and ESR parameters of the complex in aqueous solution did not correspond to those reported for its crystalline state, and in addition, those of the polymeric Cu(II) complex were different from those of the low molecular weight Cu(II) complex. It was proposed that in aqueous solution, water molecules are coordinated to the axial position of the complex where counterion molecules are present in the crystalline state, and that the structure of the polymeric Cu(II) complex is different from that of the low molecular weight Cu(II) complex due to steric hindrance of the polymeric ligand.

ISSN:0022-233X    

DOI:10.1080/00222338008056717

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The polymerization of β-alanine NCA, D, L-cis-2-aminocyclo-butane-1-carboxylic acid NCA, D, L-cis-2-amino-4-cyclohexane-1-carboxylic acid NCA, and D, L-cis-2-aminocyclohexane-1-carboxylic acid NCA was carried out in various solvents by use of triethylamine or pyridine as catalysts. The addition of these bases to a NCA solution leads to deprotonation of the NCAs and to the formation of large amounts of β-isocyanatocarboxylate ions which are detectable in the IR spectra. These isocyanates cause side reaction which prevent the formation of high molecular weight β-polyamides under all conditions studied. The role of electrophilic cocatalysts such as N-acylamino acid NCAs and chlorophenyl isocyanate was investigated. In contrast to the base-initiated polymerization of α-amino acid NCAs, the polymerization of β-amino acid NCAs is inhibited by the addition of electrophilic cocatalysts. Thus, the activated monomer mechanism is not operating in the case of β-amino acid NCAs. Various N-acyl β-amino acid NCAs were synthesized by addition of β-amino acid NCAs onto reactive isocyanates.

ISSN:0022-233X    

DOI:10.1080/00222338008056718

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Indole-containing bifunctional monomers (diacids, dialcohols, and dialdehydes) were synthesized by using as the basic nucleus two indoles attached by a tetraethylene glycol chain. These monomers were used for the preparation of polyesters, poly-amides, and polyazomethines.

ISSN:0022-233X    

DOI:10.1080/00222338008056719

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Microporous membranes were fabricated with Silastic-445 (from Dow Corning of Canada Limited) by using Luperco CST (L-CST) as catalyst and a perchlorate micropore producing additive (MPPA). Gas permeability, percent elongation, and tensile strength data show that membranes prepared with MPPA have high gas transmission rates, high percent elongation, and sufficient mechanical resistance. Scanning electron microscopic analyses reveal that the microporous silicone membranes prepared with a medium concentration of MPPA yield uniform pore distribution, the maximum pore size being <4 μm.

ISSN:0022-233X    

DOI:10.1080/00222338008056720

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

20 MHz13C-NMR (nuclear magnetic resonance) spectroscopy has been used to determine the relative concentrations of certain methacrylate and butadiene containing monomer sequence fractions in some essentially random free-radical copolymers of methyl methacrylate and butadiene. Several of the results are in good agreement with those obtained in an earlier1H-NMR study and confirm, within experimental error, that the copolymeriza-tion obeys first-order Markov statistics. The patterns of olefinic carbon resonances reveal that the progressive introduction of methacrylate units into the polymers slightly increases the trans-1,4- to cis-1,4 ratios of the butadiene units relative to that found for a pure polybutadiene prepared under similar conditions.

ISSN:0022-233X    

DOI:10.1080/00222338008056721

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0022-233X    

DOI:10.1080/00222338008056712

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor