摘要:

It is a pleasure to participate in this symposium and to celebrate Dr. Herman Mark, who has done so much for polymer science and the polymer-based industries. I am honored to be asked to talk about our debt to the polymer pioneers in the presence of a man who is indeed a charter member of such a group. As you all know, Herman Mark has written about and explained the history and substance of polymer development with great insight and clarity. And he has probably imparted that understanding to more people in more parts of the world than anyone else.

ISSN:0022-233X    

DOI:10.1080/00222338108056450

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Thermal polymerization of acrylamide has been followed by the DSC technique, and the activation energy (E) values at different stages of the fraction polymerized(a)have been determined from the exotherm of the thermograms obtained. The trend of variation of E with α shows that E remains constant up to α = 0.5 and decreases with a further increase in α. A close look at the composite nature of the exotherms, α-t, and α-T curves shows that the polymerization of acrylamide involves two processes. The first process is the formation of linear polyacrylamide and the second is the simultaneous cross-linking of the linear chains together with the formation of linear polyacrylamide. Experiments such as NH3detection by differential thermal analysis techniques and annealing studies have been made to shed further light on the polymerization process.

ISSN:0022-233X    

DOI:10.1080/00222338108056451

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Free radical-initiated copolymerization of diethyl vinyl phosphate (DEVPA) with vinyl acetate (VAc) and acrylonitrile (AN) was studied. The monomer reactivity ratios for the monomer pairs, determined at 60°C using benzoyl peroxide as an initiator, are: r1(VAc) = 0.95, r2(DEVPA) = 0.93; r1(AN) = 6.6, r2(DEVPA) = 0.049. The values of the Alfrey-Price constants, Q and e, for DEVPA were calculated to be 0.025 and 0.13, respectively, from the VAc system, and 0.026 and 0.14, respectively, from the AN/DEVPA pair. These results indicate that the general reactivity of DEVPA is almost the same as that of VAc and that the diethylphosphate group is a stronger electron-attracting group than the acetoxy group. The intrinsic viscosity and number-average molecular weight of copolymers decreased as their content of DEVPA units increased, indicating a high degree of chain transfer caused by DEVPA.

ISSN:0022-233X    

DOI:10.1080/00222338108056452

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

1,3-Cycloalkadienes of six- to eight-membered rings, such as 1,3-cyclohexadiene (1,3-CHD), 1,3-cycloheptadiene (1,3-CHpD), and 1,3-cyclooctadiene (1,3-COD), underwent spontaneous terpolymerization with styrene (St) and acrylonitrile (AN) in the presence of ZnClz, which was accompanied by cycloaddition of the diene with AN when 1,3-CHD or 1,3-CHpD was used as the diene. In the system involving 1,3-CHD as diene, the increase in ZnClz concentration increased both the rates of the two reactions and the terpolymer viscosity, while it scarcely affected the terpolymer composition. The terpolymers yielded in the terpolymerizations of 1,3-cycloalkadiene, St, and AN in the presence of ZnClz were composed of ∼50 mol% AN units and of ∼50 mol% donor monomer units, 1,3-cycloalkadiene and St. The terpolymerization was regarded as a binary copolymerization between charge-transfer (CT) complexes of 1,3-cycloalkadiene and St with AN coordinated to ZnC12, (AN)c, and the resulting monomer reactivity ratio for the 1,3-cycloalkadiene-(AN)ccomplex decreased in the order 1,3-CHD > 1,3-CHpD > 1,3-COD. Such a variation in the monomer reactivity ratios with the diene is explained in terms of two interactions in the propagation: one between the diene and (AN)cin the CT-complex and the other between the diene and a propagating radical having (AN)cas a terminal unit.

ISSN:0022-233X    

DOI:10.1080/00222338108056453

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A study was made of the polymerization of styrene initiated by azo-bis-isobutyronitrile in carbon tetrachloride solution. The overall and initiation rate as well as the degree of polymerization were found to decrease greatly with increasing dilution. Furthermore, it is pointed out that the “constant” of the chain transfer process occurring in the styrene/CCL system depends on the monomer and solvent concentrations. The solvent dependence of the chain transfer and chain propagation process is described by the hot radical theory.

ISSN:0022-233X    

DOI:10.1080/00222338108056454

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Dependence of the rate constant of initiation on the overall concentration and composition of monomer has been investigated in the free radical copolymerization of ethyl acrylate and styrene in bulk and in benzene solution at 50° C. The rate constant of initiation has been determined by the inhibition method using triphenyl-verdazil as the stable free-radical inhibitor. An equation has been derived to calculate the rate constant of initiation in a copolymerization system, where both monomers undergo a pseudounimolecular side reaction with the inhibitor. The rate constant of initiation in the copolymerization mixture is a linear composition of rate constants determined separately in the pure constituents of the system.

ISSN:0022-233X    

DOI:10.1080/00222338108056455

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Polymerizabilities of several polar vinyl monomers in the presence of imidazole (Im) have been studied in CDC13and CD3OD by NMR spectra. Acrylic acid formed a bimolecular adduct with Im as the initial adduct, while methacrylic acid was not obtained, On the other hand, methyl acrylate, methyl methacrylate (MMA), acrylamide (AAm), and acrylonitrile formed the initial adduct between Im and monomer, respectively. In these monomers, AAm and MMA gave each polymer in tetrahydrofuranat room temperature. The number-average molecular weight ([Mbar]n) of AAm polymers was determined to be in the range of 1000 to 1500, and the [Mbar]nof MMA polymers was found to be in the range of 2500 to 4500, The rate of polymerization Rpwas expressed by the equations Rp= k[Im][AAm] and Rp= k[Im] [MMA]2, respectively. The activation energy ERwas obtained by Arrheniuss's plots as ER(AAm) = 9.6 kcal/mol and ER(MMA) = 3.8 kcal/mol. These polymerization mechanisms are discussed on the basis of these results.

ISSN:0022-233X    

DOI:10.1080/00222338108056456

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Some electron-accepting compounds such as maleimide (MIm), maleic anhydride (MAn), and tetracyanoquinodimethane were found to show pronounced accelerating effects on vinyl polymerization initiated with metal chelates. The polymerization of methyl methacrylate (MMA) initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)2) and MIm was studied kinetically in benzene. The overall activation energy of the polymerization was calculated to be 11.5 kcal/mol. This value was much lower than that (17.6 kcal/mol) for the polymerization of MMA with Cu(eacac)2alone. The polymerization rate (Rp) was expressed as Rp=k[MIm]1/2[Cu(eacac)2]1/2[MMA] The first-order dependence of Rpon the monomer concentration indicated that the monomer had no participation in the initiation step, in contrast with polymerization in the absence of MIm (where a monomer concentration dependence of 1.4th order was observed). Electronic spectroscopic study revealed that a complex between MIm and Cu(eacac)2had been formed. The ligand radical, an acetylcarboethoxymethyl radical, was trapped by 2-methyl-2-nitrosopropane in the reactions of Cu(eacac)2with MIm and with MAn in benzene. From these results the mechanism of the initiation of polymerization is discussed.

ISSN:0022-233X    

DOI:10.1080/00222338108056457

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The aqueous polymerization of MMA was studied kinetically at 40° C using low concentrations of Py-SO2complex as initiator. For [Py-SO2] < 2 × 10−2mol/L, Rp∞ [PY-SO2]0.5[M]1.5, and for [Py-SO2] > 2 × 10−2mol/L, Rp∞ [Py-SO2]0,0[M]1.08. Polymerization is considered to proceed by a radical mechanism. The radical generation or the initiation step is believed to proceed through equilibrium complexation between the Py-SO2complex and monomer molecules. For [Py-SO2] < 2 × 10−2mol/L, the polymerization is characterized by bimolecular termination. Above this [Py-SO2], chain termination by a degradative initiator transfer process assumes prominence.

ISSN:0022-233X    

DOI:10.1080/00222338108056458

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Aqueous polymerization of methyl methacrylate (MMA), initiated by the potassium bromate-thioglycollic acid (TGA) redox system, has been studied at 30 ± 0.2° C under positive pressure of nitrogen. The rate is given by K[MMA] [TGA]0[KBrO3]xwhere × = 1 for lower KBrO3concentrations and 0.5 for higher KBrO3concentrations. The reaction has been studied over the 20–45°C range. The activation energy was found to be 65.72 kJ/mol (15.71 kcal/mol) in the investigated range of temperature. Inorganic electrolytes except MnSO4·4H2O and Na2C2O4depress both the rate of polymerization and the maximum conversion. All the alcohols (viz., MeOH, EtOH, iso-PrOH, tert-BuOH) and acetone depress the rate of polymerization as well as the maximum conversion.

ISSN:0022-233X    

DOI:10.1080/00222338108056459

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor