摘要:

Radical polymerization of 2-methylene-1, 3-dithiane, a six-membered cyclic dithioacetal, was carried out to give polymer possessing mainly dithioacetal unit by vinylidene Polymerization without ring-opening. The structure was confirmed by1H,13C, IR, and UV spectroscopy. On the other hand, a seven-membered cyclic dithioacetal did not polymerize radically.

ISSN:0022-233X    

DOI:10.1080/00222339108054376

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

2, 6-Dimethylphenol (2, 6-DMP) undergoes oxidative polymerization with CuCl2.2H2O-aliphatic amine complexes in a 70:30(v/v) o-dichlorobenzene-ethanol solvent. Unlike pyridine, polymerization occurs even in the absence of added base. Apart from basicity, factors such as steric effects and nature of ligand coordination to Cu(II) have profound effect on catalyst reactivity.

ISSN:0022-233X    

DOI:10.1080/00222339108054377

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A new copolyester of 3-hydroxybutyrate (3HB) and 3-hydroxypropionate (3HP) was produced byAlcaligenes eutrophusin a nitrogen-free culture solution of 3-hydroxypropionic acid, 1,5-pentanediol, or 1,7-heptanediol. The copolymer composition varied from 0 to 7 mol% 3HP, depending on the type of carbon substrates supplied. Te bacterial copolyesters were characterized by1H and13C NMR, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). The copolymers were shown to have a random sequence distribution of 3HB and 3HP units by analysis of the 125-MHz13C NMR spectra. The melting temperatures (Tm) decreased from 178 °C to 150 °C as the 3HP fraction increased up to 7 mol%. It has been found that the presence of 3HP units in polyesters accelerates the rate of enzymatic degradation.

ISSN:0022-233X    

DOI:10.1080/00222339108054378

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Styrene (St)/Methyl methacrylate (MMA) block copolymers were obtained by using a two-step procedure. In the first step, St was polymerized using 4, 4′-azobis(4-cyanopentanoic acid) (ACPA) as initiator yielding polymers with carboxyl end groups. Subsequently, photoinduced polymerization of MMA initiated by carboxyl terminated polymers in conjunction with lead tetraacetate (Pb(OAc)4) provided formation of block copolymers.

ISSN:0022-233X    

DOI:10.1080/00222339108054379

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Recently there has been great significance attached to rubber lubricants because they are associated with high output, good product quality and low energy consumption. However, existing methods for characterising lubricating property are too apparent. According to a rheological method based on the Rabinowitsch equation and capillary wail slip correction, the ‘slip coefficient–β’ and ‘slip velotity–Vs’ at the metal wall can be determined. Therefore it is possible to characterise quantitatively the external lubricating property of various rubber lubricants with β and Vs.

ISSN:0022-233X    

DOI:10.1080/00222339108054380

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Polystyrene, PSt, (Mn≈ 14 000) containing CCl3end groups was obtained by free radical polymerization of styrene, St, initiated by decomposition of azo roups of 4, 4′-azo-bis-(4-cyanopentane-trichloroacetylamide), ACPT, in dimethylformamide solution at 70°C. This polymer was used as initiator for free radical polymerization of methylmethacrylate, MMA. Free radical sites located at the end of PSt chains were generated photochemically (λinc= 436 nm) with the aid of Mn2(CO)10. St/MMA block copolymer containin 72 to 86 mol% MMA was obtained from the crude product after extraction of unreacted PSt with boilin cyclohexane. The results demonstrate that ACPT can be applied as a bifunctional initiator for the synthesis of block copolymers of type AnBmor AnBmAn, consisting of monomers A and B prone to free radical polymerization.

ISSN:0022-233X    

DOI:10.1080/00222339108054381

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A new type of macroinimers were synthesized by the capping reaction of hydroxyl groups of polyazoesters with isocyanato ethyl, methacrylate in the presence of dibutyl tin dilaurate. Macroinimers having PEG-400 and PEG-1500 units were used in the polymerization of methyl methacrylate (MMA) or styrene (S) to obtain PS-PEG or PMMA-PEG branched block copolymers at 60°C. Longer polymerization times or higher macroinimer concentrations led to cross-linked block copolymers. Similarly neat homopolymerization of macroinimers also led to the cross-linked polyethyleneglycols. The products were characterized by IR and NMR spectroscopy, viscosity measurements and fractional precipitation.

ISSN:0022-233X    

DOI:10.1080/00222339108054382

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Imidazole was employed as an anionic initiator for the homopolymerization of maleic anhydride in various solvents. Polymerization was very rapid and the obtained products have different colours varying from white to dark brown. The colour of the product was found to depend on the quantity of imidazole added, and the solvent of polymerization. Darkness of polymers are thought to be due to cross-conjugation displaying paramagnetic character. The ESR signals of dark brown polymers were more intense than the lighter ones whereas the white products had no ESR signal.

ISSN:0022-233X    

DOI:10.1080/00222339108054383

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The polymerization of acrylonitrile (AN) by polyvinyl-acetate (PVA) activated with n-BuLi results in formation of complex graft copolymers. Their molecular parameters suggest the participation of the grafted AN growing chains formed in the first stage of the overall process in the secondary reactions.

ISSN:0022-233X    

DOI:10.1080/00222339108054384

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Elastomers cured with sulfur frequently have improved mechanical properties when the curing conditions are chosen so as to give cross links that consist of chains of Sulfur atoms. If such polysulfidic cross links themselves act as elastomeric network chains, then a bimodal network is produced, albeit inadvertently. Interpretation of its properties requires, accordingly, changes in the description of the network structure, most importantly the replacement of one tetrafunctional cross link by two trifunctional ones separated by a new network chain. Illustrative calculations can be used to elucidate the deformation of such networks in terms of the molecular models much used to characterize simpler, unimodal elastomers. More detailed calculations give results in good agreement with experiment.

ISSN:0022-233X    

DOI:10.1080/00222339108054385

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor