摘要:

AbstractWith a reaction conducted on model molecules with low amounts of catalysts and at low temperatures (170–225°C), it was shown that esterification is mainly catalyzed by the carboxylic acid groups and by the titanium derivatives; the activity of the other metals can only be seen when the concentration in carboxylic acid groups is low. In the alcoholysis reaction, the activity of Zn, Mn, and (much less) Ti, decreases when the percentage of ester in the reaction medium decreases, whereas it is the opposite with Sb. Moreover, Zn, Mn, and Co are sensitive to trace amounts of carboxylic groups (their activity decreases), whereas Ti is much less affect

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271101

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

Abstract4‐Methacryloxy‐2,3,5,6‐tetrabromobenzyl phosphonates (MTBBP) are prepared by the reaction of corresponding 4‐hydroxy‐2,3,5,6‐tetrabromobenzyl phosphonates (HTBBP) with methacryloyl chloride. Comparisons of flame retardancy among the copolymers of methylmethacrylate (MMA) with MTBBP or with 4‐methacryloxy‐2,3,5,6‐tetrabromotoluene(MTBT) and the mixture of poly(methyl methacrylate) (PMMA) with triphenyl phosphite reveal that the combination of phosphorus and bromine elements produces a synergistic effect on flame retardancy, and the chemical grafting of the fire‐resistant elements into the polymer backbone gives a better effect than the physical mixing of their compounds with polymer. The unsatisfactory results of homopolymers of the synthesized methacrylate monomers prepared by free radical polymerization in solution may be due to their less reactivities; however, they can readily copolymerize with a liquid vinyl monomer such as MMA by means of

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271102

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractA new approach is presented to calculate both the distribution of particles withiradicals and the average number of radicals per particle in emulsion polymerizations carried out using oil‐soluble initiators. The convergence and accuracy of the approach were examined. It was found that, in agreement with previously published experimental results, the present approach predicts a kinetic behavior similar to that found for water‐soluble initiators. This effect is primarily due to the desorption of initiator radicals from the polymer particles rather than the contribution of the fraction of oil‐soluble initiator dissolved in the aqueous

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271103

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe optically active polynucleotide analogs were prepared by grafting nucleic acid base derivatives onto poly(vinyl alcohol). The (R)‐ethyl 2‐(5‐bromouracil‐1‐yl)propanoate was obtained either by reaction of 5‐bromouracil sodium salt with (S)‐ethyl 2‐[(methylsulfonyl)oxy]propanoate or reaction of 5‐bromouracil with (S)‐ethyl lactate in the presence of triphenyl phosphine and diethyl azodicarboxylate. Subsequent hydrolysis of the ester is aqueous acid provided the optically pure (R)‐bromouracilypropanoic acid. The monomer model compounds were prepared by an esterification reaction of the pendant groups with 3‐pentyl alcohol in the presence of dicyclohexylcarbodiimide and a catalytic amount of 4‐pyrrolidinopyridine. Poly(vinyl alcohol) underwent reaction with the (R)‐bromouracilylpropanoic acid or the (R)‐adeninylpropanoic acid in the presence of dicyclohexylcarbodiimide and a catalytic amount of 4‐pyrrolidinopyridine. The resulting polymers were optically active and percents gr

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271104

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractUndecyl and phenyl oxazolines were synthesized. They were copolymerized in different mole ratios using methyl nosylate as initiator. A series of di‐ and triblock copolymers with narrow molecular weight distributions as indicated by GPC were obtained. A three‐armed block copolymer was also obtained by using 1,3,5‐tris(bromomethyl)benzene as initiator. When the nonpolar undecyl block crystallized as a coating, the critical surface energy approached 21.0 dyn/cm, and the contact angle of water on the surface could be higher than 107°. The melting point increased as the chain length of crystallizable undecyl block increased, and the melting peak on DSC was very sharp when the length was equal to or longer than 25 monomer units. When these copolymers were coated on substrates, the work of adhesion with pressure sensitive adhesives was greatly r

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271105

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractTwo component interpenetrating networks (IPNs) of the SIN type (simultaneous interpenetrating networks), composed of a polyisocyanurate network and a star‐shaped nylon 6, were made. The overall polymerization rates and physical properties for reaction injection molding (RIM) have been studied by the quasi‐adiabatic process. In order to model the actual rapid molding conditions, time versus temperature reaction profiles were measured, and the relative rates of polymerization subsequently determined from these d

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271106

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe anionic polymerization of ϵ‐caprolactam (CLM) has been shown to proceed at high reaction rate when catalyzed by metallic lactamates and initiated by acyllactams. The role of initiator and catalyst concentration on the process of ϵ‐caprolactam anionic polymerization has been explored, with the aim of selecting the most suitable experimental conditions for reaction injection molding (RIM). The overall polymerization rates and physical properties for reaction injection molding of star‐shaped nylon 6 homopolymer have been studied by the quasi‐adiabatic process. In order to model the actual rapid molding conditions, time vs. temperature reaction profiles were measured, and the relative rates of polymerization subsequently determined from t

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271107

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

Abstractα‐Methoxyphenylmethylium hexachloroantimonate was used as a novel initiator for the polymerization of α,β‐disubstituted oxiranes such as cyclohexene oxide (CHO) and 2‐butene oxide (transandcis) (2‐BO) at −78°C with dichloromethane or dichloromethane‐toluene mixtures as solvents. The CHO polymerization mixture became turbid and the polymer precipitated in dichloromethane. The CHO polymerization proceed quantitatively in dichloromethane–toluene mixtures. The molecular weight distribution of polyCHO obtained was bimodal regardless of the solvent used. The polymerization oftrans‐2‐BO was heterogeneous in both dichloromethane and dichloromethane–toluene mixture. The polymerization mixtures ofcis‐2‐BO were transparent but reached a limit yield which was less than the polymer yield oftrans‐2‐BO. Furthermore, the microstructure of the poly2‐BOs were analyzed by Vandenberg's method and the results confirmed Vandenberg's finding that inversion of configurati

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271108

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractMiniemulsion copolymerization of 50 : 50 weight fraction of styrene–methyl methacrylate monomer, using hexadecane as the cosurfactant, was carried out in both unseeded and seeded polymerizations. Effects of the hexadecane concentration and the ultrasonification time on the conversion–time curves and particle size of the final latex were investigated for unseeded polymerization. The kinetic and particle size distribution results showed that an increase in hexadecane concentration and ultrasonification time cause faster polymerization rate and smaller particle size. The mechanism of mass transport from miniemulsion droplets to polymer particles was also investigated for seeded polymerization. For this purpose a monomer miniemulsion was mixed with a fraction of a previously prepared miniemulsion latex particles prior to initiation of polymerization, using residual oil‐soluble initiator in the seed latex. The concentration of hexadecane and a water‐insoluble inhibitor (2,5 di‐tert‐butyl hydroquinone) in the miniemulsions were the main variables. Seeded polymerizations were also carried out in the presence of miniemulsion droplets containing a water‐insoluble inhibitor and water‐soluble initiator. The inhibitor concentration and the agitation speed during the course of polymerization were the experimental variables. The kinetic and particle size results from these seeded experiments suggested that collision between miniemulsion droplets and polymer particles may play a major role in the transport of highly water‐in

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271109

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY

摘要:

AbstractSynthesis of novel triblock, polycaprolactone‐b‐polydimethylsiloxane (PDMS) and poly(2‐ethyl‐oxazoline)‐b‐PDMS copolymers were demonstrated. These materials were obtained via the ring‐opening polymerization of ϵ‐caprolactone or 2‐ethyl‐2‐oxazoline monomers by using organofunctionally terminated PDMS oligomers as initiators and comonomers. Segment molecular weights in these copolymers were varied over a wide range between 1000 and 2000 g/mol and the formation of copolymers with desired backbone compositions were monitored by1H‐NMR spectroscopy and GPC. DSC and TMA studies showed the formation of two phase morphologies with PDMS (Tg, −120°C) and polycaprolactone (Tm, 50–60°C) or poly(2‐ethyl‐2‐oxazoline) (Tg, 40‐60°C) transitions respectively. The use of polycaprolactone‐b‐PDMS copolymers as surface modifying additives in polymer blends were also investigated. When these copolymers were blended at low levels (0.25–10.0% by weight) with various commercial resins such as, polyurethanes, PVC, PMMA, and PET, the resulting systems displayed silicone‐like, hydrophobic surface properties, as determined by critical surface tension measurements or water contact angles. The effect of siloxane content, block length, base polymer type and mor

ISSN:0887-624X    

DOI:10.1002/pola.1989.080271110

出版商:John Wiley&Sons, Inc.    

年代:1989

数据来源: WILEY