摘要:

Recalculation of reactivity ratios has led to improved Q and e values for a variety of monomers.

ISSN:0022-233X    

DOI:10.1080/00222338008081031

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

In attempting to improve the evaluation of Q and e values, some 900 reactivity ratios were recalculated.

ISSN:0022-233X    

DOI:10.1080/00222338008081032

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Thermal decomposition and glass-transition temperature studies have been carried out on poly-p-methylstyrene (PpMeS) with the DSC-2 differential scanning calorimeter. The undecomposed and decomposed polymers were analyzed by gel-permeation chromatography (GPC), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). Decompositions of PpMeS under isothermal conditions during 50-min periods in the 25–330°C temperature range did not affect Mwvalues; however, Mnvalues decreased from 5.1 × 104to 1.5 × 104. The decomposed polymers following treatments at temperatures above 330°C are only partially soluble in THF, o-C6H4Cl2, and CCl4. These products may therefore contain certain crosslinked materials. The results of the IR analyses show that in the polymers decomposed at temperatures above 330°C, the aromatic content is lower than that observed for polymers decomposed in the 25–330°C temperature range. The variation of Tge(at q = l°K/min) with Mnobeys the relation; Tge(K) = 384–2.65 × 105/Mn. The value of 384° K for the Tgof PpMeS at infinite molecular weight is close to that found for PS (379°K) but is far below that (453°K) obtained for PαMeS. This illustrates the relative importance of the methyl substitution in the vinyl chain as compared to that in the aromatic rings.

ISSN:0022-233X    

DOI:10.1080/00222338008081033

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Immobilization of enzymes by radiation-induced polymerization has been studied at low temperatures by use of various hydrophilic and hydrophobic glass-forming monomers such as hydroxy-alkyl methacrylate and poly(ethylene glycol diacrylate). Activity yield of the immobilized enzyme depends on the monomer concentration in polymerization. In the immobilized enzymes with strongly hydrophobic matrices, the activity shows a maximum at an optimum monomer concentrations in a certain stage of repeated usage for the enzyme reaction. The decrease of activity with repeated use is very little in strongly hydrophobic systems, particularly in diethylene glycol diacrylate polymer matrices. The hydrophobic polymer-enzyme composite has the microsphere form. In the present method, a model scheme for immobilization mechanism is proposed, which is compared with that formed in the polymerization of a nonglass-forming monomer system and also by the solution polymerization at higher temperatures.

ISSN:0022-233X    

DOI:10.1080/00222338008081034

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Immobilization of enzymes by radiation-induced copolymerization was studied at low temperatures by use of various comonomer systems consisting of 2-hydroxyethyl methacrylate and other more hydrophilic or hydrophobic comonomers. The matrices obtained by copolymerization with more hydrophilic and more hydrophobic comonomers decreased the porosity in the matrix equally. However, the activity yield of the immobilized enzyme showed different changes with repeated use in the more hydrophilic and more hydrophobic matrices. That is, the initial activity decreased rapidly with repeated use owing to the enzyme leakage from the matrix, in the increased hydrophilic matrices. On the other hand, in the more hydrophobic matrices enzyme leakage was completely retarded and activity did not change with repeated use. Moreover, the activity yield showed a maximum at a certain monomer composition in the copolymerization with hydrophobic comonomer. Finally, it was found that the maximum activity yield of the hydrophobic matrices was larger in general than that of the hydrophilic copolymer matrices.

ISSN:0022-233X    

DOI:10.1080/00222338008081035

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Antimony (V) polycobalticinium esters, where the anion was PF6−, Cl−, Br−and NO3−, were synthesized. A number of factors were found to be important in the synthesis, including anion exchange and pH. The products containing PF6−are oligomeric (DPw= 7) whereas the other products are di-and trimeric. The products undergo oxidative degradation beginning about 100 to 225°C. They are near semiconductors with resistivities about 105to 107ohm-cm.

ISSN:0022-233X    

DOI:10.1080/00222338008081036

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The use of preformed poly(ethylene oxide) (PEO) and carboxyl-terminated polybutadiene (CTPB) for the preparation of block polymers is reported. Block polymerization was carried out by esterification and by coupling of equimolar amounts of these polymers with 2,4-toluene diisocyanate (TDI). When esterification was carried out, conversion of the two preformed polymers and block polymer composition varied with reaction temperature, catalyst used, and molecular weight of the PEO. Full conversions were not obtained. Better results were achieved when the preformed polymers were coupled with TDI. Tensile properties and water absorption capability of these block polymers were determined. Hydrogels with high water content up to 82% were obtained.

ISSN:0022-233X    

DOI:10.1080/00222338008081037

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

α-Methylstyrene (α-MS) and isobutyl vinyl ether (IBVE) were copolymerized by using the H2O/EtAlCl2initiator system and CH2Cl2and CH3Cl solvent in the temperature range from -30 to -90°C. As compared to homopolymerization of α-MS, both yields and molecular weights are reduced upon addition of small amounts of IBVE to the feed. The reactivity ratios were calculated by the method of Kelen and Tödös as well as the Fineman and Ross method, and the combined effect of change of solvent and temperature on reactivity ratios was determined. Effects of feed composition and temperature on the copolymer yield, composition, and number-average molecular weightMnwere studied in detail.Mnshowed a novel exponential dependence on the IBVE concentration in the feed. The overall activation energies of molecular weight were determined from the Arrhenius plots for both homo-and copolymerization systems. Based on these and the yield data, a speculation is made regarding reaction mechanism for molecular weight control. NMR and DTA data are reported, which establish the random nature of the copolymers.

ISSN:0022-233X    

DOI:10.1080/00222338008081038

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Pressure-volume (P-V) behavior and radiation-induced polymerization of methyl and n-butyl acrylic esters (MA and BA, respectively) were studied up to 7000 kg/cm2at 20°C. The P-V isotherms broke at 1900 and 1200 kg/cm2for MA and BA, respectively. The P-V isotherm for MA was not smooth in the pressure range between 3500 and 4000 kg/cm2. The polymerization behavior varied with change in the P-V behavior; the polymerization rates were maximum at 1800 kg/cm for MA and 1000 kg/cm2for BA, and then minimum at 1900 kg/cm2for MA and 1100 kg/cm2for BA. The polymerization rates increased again above the pressures giving the minimum rates up to about 3000 kg/cm2. Above 3000 kg/cm2the pressure dependence of the rates decreased up to 4000 and 4500 kg/cm2for MA and BA, respectively. Above these pressures, the pressure dependence of polymerization rates increased again. The P-V isotherms of as-polymerized polymer-monomer coexistence systems showed characteristic behavior near the polymerization pressure. From a comparison of these polymerizations and P-V behavior with those of methacrylic esters, we propose that acrylic esters align at high pressure and that freedom of rotation of ester group plays an important role in the mode of pressure-induced alignment of monomer molecules.

ISSN:0022-233X    

DOI:10.1080/00222338008081039

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Elementary features of the absorption behavior of oligo[1-(N-phenylcarbamoyl)aziridine] were studied. The oligomeric host shows interesting binding specificities for a variety of organic compounds. The binding process for hydrogen bond-donating compounds typified by aromatic amines is found to be related to “swelling” of the solid oligomer host, and the binding specificity may be closely related to the essentially flexible or mobile nature of the oligomer host. For polar substrates containing S˭O the absorption occurs in a less swollen state, resulting in a hindrance of absorption for aromatic S˭O compounds. Selective absorption from binary systems, exemplified with S˭O compounds, can be attained as expected from the corresponding single-substrate systems as far as at low substrate concentrations.

ISSN:0022-233X    

DOI:10.1080/00222338008081040

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor