摘要:

The Meyer/Misch and related models were found to be the most energetically stable for the crystalline structure of cellulose I. The cellobioside structure is the monomer of cellulose I because structures having cellobiose as monomer have proven to be energetically much less stable. The conformation of the monomers terminating the crystalline zone and initiating the amorphous zone have been accurately described. The cause and mechanism of termination of the crystalline zone have been identified and described. A few new considerations regarding the conformation and appearance of the amorphous zones in cellulose I, in which the chains are in helicoidal conformations, are discussed. The predominance of van der Wads and H-bond interactions in the crystalline zone have been confirmed, and the H-bond values, locations, and distribution in the crystalline zone have been accurately mapped.

ISSN:0022-233X    

DOI:10.1080/00222338508063302

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Propargyl alcohol was codimerized with acetylene, and 4-penten-2-yn-1-o was obtained. Propargyl alcohol was cotrimerized, but the main product was the homotrimer whether the comonomer was vinylacetylene or 2-methylbutenyne. The cotrimerization of 1,1-dimethylpropargyl alcohol was more easily regulated. With acetylene it gave the m- and p-di-α-hydroxypropylbenzenes.

ISSN:0022-233X    

DOI:10.1080/00222338508063303

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cross-linked poly(4-vinylpyridine) was converted to its borane complex by different methods. The exchange reaction with BH3-THF; the reaction of boron trifluoride iodine, and bromine polymer complexes; as well as the hydrochloride derivative with sodium borohydride were investigated. Polymers with a high borane content were obtained. The borane content was dependent on the cross-linking level and on the method of preparation. The hydrolytic stability of the borane-bound polymer was higher than that of pyridine-borane. The cross-linked poly(4-vinylpyridine)-borane showed a high degree of stability toward hydrolysis under acidic conditions. Hydrolysis in acidic media was found to be an autoaccelerated reaction.

ISSN:0022-233X    

DOI:10.1080/00222338508063304

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Cross-linked poly(4-vinylpyridine)-borane was successfully used for the reduction of aldehydes and ketones to the corresponding alcohols. Reduction was carried out in protic and aprotic acidic media at room temperature. Polymer reactivity depends on solution pH. Due to the relative high hydrolytic stability of the borane-bound polymer, reduction can be carried out in pH 1 buffer solution and in acetic acid. A low degree of cross-linking did not affect the polymer reactivity. Complete reduction of carbonyl compounds can be reached in the presence of excess of borane-bound polymer at a 1:1 reactants molar ratio. Only two of the borane hydrides are available for reduction; the third one is consumed by hydrolysis of the partially reacted borane derivatives formed during and after reduction. The chemoselectivity in the competitive reduction of cyclohexanone and other ketones as well as acetophenone and benzaldehyde with cross-linked poly(4-vinylpyridine)-borane was investigated. The cross-linked polymer borane was found to be a much better chemoselective reduction agent than its low molecular weight analog pyridine-borane. Chemoselectivity of this polymer is as good as that of available low molecular weight chemoselective reduction agents.

ISSN:0022-233X    

DOI:10.1080/00222338508063305

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The present paper deals with the radical polymerization kinetics of the systems MU-AIBN-Bz-50°C and MMA-AIBN-BrBz-50°C. The rate of initiation and the k2/√k4value were determined in a broad range of monomer concentrations. The initiation rate constant was found to be independent of the concentration of solvent and monomer. In the system MMA-Bz the k2/√K4value does not change with dilution, while in the system MMA-BrBz it depends on the viscosity of the initial monomer-solvent mixture.

ISSN:0022-233X    

DOI:10.1080/00222338508063306

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An electron spin resonance study of the intermediate radicals formed in the cyclopolymerization of certain nitrogen-containing monomers has been carried out. An initiation radical, both in N-(p-bromophenyl)dimethacrylamide (BrPhDMA) and sym-dimethacryloyldimethylhydrazine (DMMH), could be observed. The crystalline structure of DMMH is not known at present, but the comparison of the crystalline structure of BrPhDMA with that of N-methyldimethacrylamide suggests that the crystalline structure in these cyclization reactions is very important, In the glassy state of BrPhDMA, an anion radical of the methacryl group was detected as was the case in the glassy state of propyl- and benzyldimethacrylamides. It is significant that only the 5-membered cyclic radical was detected in the glassy state of BrPhDMA, because only the non-cyclic initiation radical was observed in irradiated crystalline BrPhDMA at -196°C, and only the 5-membered cyclic radical was detected in propyl- and benzyldimethacrylamide in both the crystalline and glassy states.

ISSN:0022-233X    

DOI:10.1080/00222338508063307

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Acenaphthylene (ACN) has been polymerized at 60° C using benzoyl peroxide labeled with carbon-14 and tritium as the Lnitiator. End-group analyses show a very high proportion of benzoate groups among the incorporated initiator fragments. It is deduced that ACN is much more reactive than most other monomers toward the benzoyloxy radical. There is evidence that transfer to benzoyl peroxide is significant during the polymerization of ACN.

ISSN:0022-233X    

DOI:10.1080/00222338508063308

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The polymerization of acrylic acid with NO2in benzene was carried out. The initial rate of polymerization shows first-order dependence on the monomer concentration and half-power dependence on the initiator concentration. The molecular weight of polymers also shows dependence on monomer and initiator concentrations. The overall activation energy of polymerization was found to be about 22.7 kcal/mol. The kinetic mechanism of polymerization is discussed.

ISSN:0022-233X    

DOI:10.1080/00222338508063309

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The photopolymerization of methyl methacrylate (MMA) in visible light was kinetically studied at 40° C using the acridone-chlorine (acridone-Cl2) combination as the photoinitiator. The polymerization was found to proceed via a free-radical mechanism, and the radical generation process was considered to follow an initial com-plexation reaction between monomer (MMA) and each initiator component (acridone and Cl2). Kinetic data indicated a lower order dependence of RPon initiator concentration (initiator exponent < 0.5), and the monomer exponent varied from about 1.00 to 1.25, depending on the nature of the solvents used. Initiator-dependent chain termination was significant along with the usual bimolecular mode of chain termination. The nonidealities in this system are analyzed.

ISSN:0022-233X    

DOI:10.1080/00222338508063310

出版商:Taylor & Francis Group    

年代:1985

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:10.1080/00222338508063301

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor