摘要:

AbstractHigh‐resolution nuclear magnetic resonance has been used in order to investigate the base‐catalyzed reaction of formaldehyde with urea in deuterium oxide. We investigated the effects of temperature and concentration on the chemical shift of glycol species in formalin under basic condition. Assignment of all the signals appearing in the addition reaction was completed. The formation ofN,N‐dimethylolurea, uron, monomethyloluron, and dimethyloluron was observed for the first time, as well as the formation of monomethylolurea,N,N′‐dimethylolurea, and trimethylolurea, which had been observed previously: the formation of presumptive tetramethylolurea could not be observed. The rate constants and equilibrium constant for urea, monomethylolurea,N,N′‐ andN,N‐dimethylolurea, and trimethylolurea were estimated by analysis of the decomposition reactions of monomethylolurea andN,N

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140211

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractA method for the preparation of poly(vinyl chloride)‐β,β‐d2(PVC‐β,β‐d2) as a model for the investigation of the mechanism of chlorination and of the CPVC structure has been suggested. The conditions of preparation of deuterated intermediates of a multistage synthesis of vinyl chloride‐β,β‐d2and of suspension‐polymerized PVC‐β,β‐d2have been described including the mass balance. Malonic acid was used as the starting compound. Tacticity values of a sample of PVC‐β,β‐d2and its infrared and NMR spectra are presented and compa

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140212

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe raactivity changes which occur in diamine monomers during polymide formation were investigated. A series of aromatic diamines were reacted with three aromatic anhydrides (including 1,4,5,8‐naphthalene tetracarboxylic dianhydride) under different conditions and the products isolated and identified. There was a great range of reactivity changes depending on the conjugation between the two amino groups of the diamine monomer. For highly conjugated groups, imide formation at one group can prevent any reaction at the other, and hence polymer formation is curtaile

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140213

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe polymerization of methyl methacrylate was carried out in water at various concentrations of sodium bisulfite, ferric oxide, and methyl methacrylate at 30, 40, and 50°C. The effect of ferric oxide on the rate of polymerization was studied at 50°C. Rates of polymerization increased in the presence of ferric oxide. For example, the rate of polymerization increased from 3.4 × 10−5mole/l.‐sec to 11.8 × 10−5mole/l.‐sec when the ferric oxide concentration was varied from 0 to 15 g/l. water. The molecular weight of the polymer decreased from an average of 1.4 × 106in the absence of ferric oxide to 2.8 × 105when the ferric oxide was present. The variation of molecular weight of the polymers with temperature and conversion was studied. At a fixed conversion of 80%, the average molecular weight decreased from 3.4 × 105at 30°C to 2.2 × 105at 50°C. The average molecular weight was also found to increase with increasing monomer and initiator concentrations. It increased from 8.1 × 104to 5.3 × 105and from 3.4 × 105to 8.9 × 105as the initiator and monomer concentrations increased from 0.01 to 0.05 mole/l. and from 0.235 to 0.705 mole/l., respectively. The apparent energy of activation for the polymerization was found to be 15.6 and 9.7 kcal/mole in absence and in presence of ferri

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140214

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractAqueous poly(vinyl alcohol) solutions were crosslinked via electron‐beam irradiation to form transparent hydrogels of varying crosslinking densities. Typical crosslinked hydrogels withMcbetween 3500 and 8000 were weak, easily shattered, nonextensible materials with very low tensile moduli (up to 70 psi) and tensile strengths at break (less than 10 psi). Reinforcement by induction of partial crystallization was accomplished by a two‐stage drying process, consisting of a slow dehydration stage at room temperature and an annealing stage at elevated temperatures, which was mainly responsible for the introduction of the crystallites. The swollen hydrogels after the annealing process had crystallinities widely varying between 30 and 65% and polymer volume fractions between 30 and 60%, depending on the temperature‐time history of the specimen. These materials showed greatly improved mechanical properties (modulus, ultimate tensile strength, tear strength), as compared to the uncrystallized hydr

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140215

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe Flory interaction parameter χ1of poly(vinyl alcohol)‐water systems has been estimated as a function of temperature and volume fraction of PVA, the polymer having been crosslinked from solutions of the same in water. Values are reported for temperatures between 0°C and 90°C and polymer volume fractions between 0.03 and

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140216

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractStyrene was copolymerized in bulk with vinyltriethoxysilane at 80°C and vinyltriacetoxysilane at 60, 80, and 100°C with the use of benzoyl peroxide as an initiator at low conversions. Copolymer composition was determined from the silicon content and reactivity ratios were calculated by the conventional scheme of copolymerization. The lowr1value (styrene) in the styrene‐vinyltriacetoxysilane system (St–VTAS) as compared to styrene‐vinyltriethoxysilane (St–VTES) copolymerization may be attributed to higher reactivity of VTAS towards the polystyryl radical. Further, in the St–VTAS system,r1tends to decrease with increasing polymerization temperature. The influence of silicon comonomer on properties of the copolymers (intrinsic viscosity, solubility, dielectric and thermal behavior)

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140217

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe spectroscopic and physical properties of poly(vinylferrocene) prepared by free‐radical polymerization in benzene are discussed. The results obtained in these studies are in accord with the kinetic analysis of the polymerization reactions in benzene. ESR spectroscopy shows that the polymer is paramagnetic and contains a species which is identified by Mössbauer spectroscopy as an ionically bound complex of Fe(III) in a high spin (3d5) configuration. The concentration of this species is shown to be dependent upon kinetic parameters. Magnetic susceptibility measurements show that the polymer does not contain any oxidized ferromagnetic impurities. Infrared spectroscopy indicates that the polymer contains vinylidene groups. The presence of these groups is explained by chain transfer to monomer followed by reinitiation. Ultraviolet spectroscopy also suggests the presence of unsaturation in the polymer. Gel‐permeation chromatography indicates that poly(vinylferrocene) is branched even at low conversions. The effect of transfer reactions and the intramolecular electron transfer termination of the chain radical on the structure of poly(vinylferrocene) is discussed. The glass transition temperature and thermal stability of the polymer are also exam

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140218

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractThe chemical stress relaxation of crosslinked polymers had long been studied. The chemorheology of linear polymers is difficult to study because molecular flow by diffusion is generally much more rapid than relaxation or flow caused by chemical reaction. Our previous paper dealt with the chemorheology of linear polymers on taking such physical flow into consideration. By using another modified expression suggested by Tobolsky, good consistency between the theoretical chemical stress relaxation curve and an experimental one was obtained for polydisperse polystyrene and the commercial polystyrene used.

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140219

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY

摘要:

AbstractPolybutadiene was successfully metalated by use oftert‐butyllithium activated with alkoxides of Group I metals without chain degradation. The metalated polymer was grafted with styrene and 1,3‐butadiene to give novel graft copolymers of varying microstructure. This metalating system was found to be highly efficient; however, its catalyst effectiveness is less than that of organolithium‐TMEDA metalation

ISSN:0360-6376    

DOI:10.1002/pol.1976.170140220

出版商:John Wiley&Sons, Inc.    

年代:1976

数据来源: WILEY