摘要:

AbstractThe kinetics of the basic hydrolysis of several poly(phenyl methacrylates) with different substituents in the aromatic ring were investigated. Using Keller's equations to describe the effect of neighboring groups on the kinetics of side‐group reactions in polymers, we computed the corresponding rate constants which correlated well with Hammett's substituent constant

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201201

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractA commercially available densimeter with a vibrating stainless steel tube was used as a detector in the GPC analysis of styrene/methyl methacrylate copolymers under normal GPC operational conditions. The densimeter was thermostated to ±0.001°C and sample injection concentrations were 4.0 mg/mL. The copolymer samples were polydisperse in molecular weight but uniform in composition. A refractive index detector and the densimeter detector produced comparable estimates of the parameters of the molecular weight distributions. The densimeter is less sensitive to the effects of variations in copolymer composition than differential refractive index or ultraviolet detectors. The only serious drawback to the densimeter is a relative lack of sensitivity. Variations in composition of styrene/methyl methacrylate copolymers over a fairly wide range have no signficant effect on the relation between gel permeation chromatographic elution volume and copolymer molecular weight. In general, however, conventional means of summarizing these data are not applicable to compositionally heterogeneous mixtures. Instrumental and data‐handling solutions to this problem are discus

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201202

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

Abstract13C‐NMR spectra of bulk acrylonitrile‐butadiene‐styrene (ABS) resin are reported. The styrene‐co‐acrylonitrile (SAN) carbons can be observed selectively by using high‐power proton decoupling, cross polarization, and magic angle spinning (MAS). The polybutadiene (PBd) carbons can be observed selectively by using low‐power proton decoupling, with or without MAS. Methods and conditions for using13C‐NMR to quantify the amount of PBd in solid ABS resins are developed. The13C‐NMR results and results from iodine monochloride titrations for PBd content are in good agreement. Resonances of PBd in ABS in the solid state are assigned on the basis of triad sequences of cis, trans, and vinyl‐1,2 geometric isomers of butadiene. Computational methods are set forth for measuring directly from the13C‐NMR spectra the percent of cis, trans, and vinyl‐1,2 isomers in PBd in the ABS resin. The NMR measurement of PBd microstructure appears to be preferable to infrared (IR) determinations. Relaxation parameters (T1and NOE) are reported for PBd in bulk ABS as a function of temperature and are analyzed in terms of a distribution of rotational correlation times. These relaxation parameters are similar to those of nongrafted PBd and indicate that the local motions in grafted and non

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201203

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractBy use of carbon black that contained alkali metal carboxylate (COOM; MLi, Na, K, Rb, or Cs) group as catalyst the anionic polymerization of β‐propiolactone (PL) was carried out at 50°C and the grafting of polyester onto the carbon black surface was investigated. Carbon black that contained COOM group was prepared by the reaction of carboxyl group on the surface with corresponding alkali metal hydroxide and was able to initiate the anionic ring‐opening polymerization of PL. The carbon black obtained from the reaction gave a stable colloidal dispersion in an organic solvent. It was confirmed that the polyester formed was grafted effectively onto the surface; for instance, by using carbon black that contained COOK group as catalyst the grafting ratio was increased to 145% (viz., 1.45 g of polyester was grafted/1 g of carbon black) with an increase in conversion. Furthermore, the effect of alkali metal countercation (M+) on the polymerization was studied. The initiating activity of COOM group on the surface increased in the following order: COOLi<COONa<COOK<COORb<COOCs. This order was in agreement with that of increasing electropositivi

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201204

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe second moments of the ESR signals obtained from poly(p‐phenylene) (PPP) and deuterated PPP were measured at 9.5 and 35 GHz. The theoretical and experimental contributions to the second moments were considered. It is shown that for deuterated PPP, deuteron hyperfine splitting makes a negligible contribution to the observed second moment. The proton hyperfine contributions to the second moments of the radical species in PPP andp‐sexiphenyl were estimated and it was concluded that the unpaired electron was delocalized over only 2‐4 phenylene units. A rationale is offered in terms of polarons present as defects in the PPP c

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201205

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractESR data for poly(p‐phenylene) (PPP) prepared from benzene and catalyst‐oxidant systems were compared with data for PPP obtained by a variety of other methods. The results were similar, except for the Yamamoto preparation, and comparable to the spin densities for heterocyclic polymers of thiophene, pyrrole, and selenophene. Deuterated PPP from C6D6showed significant differences in properties, in comparison to ordinary PPP, in relation to molecular weight, color, solubility, and spins/g in electron spin resonance (ESR). The implications are discussed with regard to the mechanism of benzene polymerization by AlCl3‐

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201206

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe kinetics of polymerization of acrylamide (AM), acrylic acid (AA), and acrylonitrile (AN) initiated by the redox system Mn3+–diglycolic acid (DGA) was studied. All three systems followed the same mechanism; namely, initiation by an organic free radical arising from the oxidation of diglycolic acid and termination by the interaction of polymer radicals with Mn3+ion. The rate coefficientski/k0andkp/ktwere related to monomer and polymer radical reactivity, respectively. An inverse relation between monomer and polymer radical reactivity was observed. Monomers with higher Q values gave higherki/k0values but lowerkp/ktvalues. Theevalues of the monomers were important in determining the reactivities of monomers with nearly the sameQvalue

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201207

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractIt was found that structurally isomeric polymers were formed by the ring‐opening polymerization of β‐(2‐acetoxy ethyl)‐β‐propiolactone with (EtAlO)nand Et(ZnO)2ZnEt catalysts; that is, the Al catalyst catalyzed normal polymerization which led to poly‐β‐ester and the Zn catalyst formed isomerized poly‐β‐ester as the main product. The polymer structure was determined by nuclear magnetic resonance (NMR), T1‐value, thermal decomposition product, and (Tg). The NMR studies for the monomer–catalyst systems indicated that the Al catalyst interacted predominately with the lactone group, whereas the Zn catalyst interacted with the side‐chain ester group. These site‐selective interactions could be related to the difference in the stereoregulation by the two catalysts during the poly(β‐ester

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201208

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractPolydimethylsiloxane oligomers with silanol ends condense in aqueous dispersion under mild conditions to form high polymers in the presence of sulfonic acid surfactants. The process follows a second‐order rate law in silanol if reversibility is taken into account. The second‐order rate constant is proportional to the area at the oil–water interface and is a complex function of surfactant concentration. The principal driving force is the heat of condensation of the water produced in the polymerization. A mechanism paralleling surface catalysis is offered in which a termolecular complex that consists of two surfactant molecules and one silanol end group reacts bimolecularly at the oil–water in

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201209

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThis article deals with the kinetics and mechanism of acrylonitrile (AN) polymerization initiated by Cu(II)–4‐anilino 3‐pentene 2‐one[Cu(II)ANIPO], Cu(II)–4‐p‐toluedeno 3‐pentene 2‐one [Cu(II)TPO], and Cu(II)–4‐p‐nitroanilino 3‐pentene 2‐one [Cu(II)NAPO] in bulk at 60°C. The polymerization is free radical in nature. The exponent of initiator(I) is ≃ 0.5. The initiation step is a complex formation between the chelate and monomer and subsequent decomposition of the intermediate complex giving rise to free radical and Cu(I). This is substantiated by ultraviolet (UV) and electron spin resonance (ESR) studies. The activation energies and kinetic and chain transfer cons

ISSN:0360-6376    

DOI:10.1002/pol.1982.170201210

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY