摘要:

Radiation polymerization of large crystals of chloroprene formed within the temperature range -130 to -180°C has yielded the stereoregular trans-1,4-poly(2-chloro-1,3-butadiene). The monomer was found to have a glass transition temperature of ca. -180°C. Polymerization of monomer rapidly cooled to below -180°C was difficult and gave only structurally irregular polymer in low yield.

ISSN:0022-233X    

DOI:10.1080/00222337008059515

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Polyisoprene popcorn polymer has been shown to exhibit the typical properties of this class of polymers–insolubility and ability to propagate at a rate dm/dt-km. In contrast to butadiene popcorn, polyisoprene popcorn polymer (PIP) does not show marked variations in growth activity with growth generations.

ISSN:0022-233X    

DOI:10.1080/00222337008059516

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Iodobenzene dichloride or diacetate initiates the polymerization of 2,6-dimethylphenolate anion to poly [oxy(2,5-dimethyl)-l, 4-phenylene]. Electron spin resonance spectroscopy was used to identify the polymeric radical that is the growing chain. Infrared and NMR spectroscopy identified the final polymer. The mechanism proposed is probably applicable also to other phenol oxidation processes yielding substituted poly(oxyphenylenes).

ISSN:0022-233X    

DOI:10.1080/00222337008059517

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The heterogeneous anionic polymerization of ethylene oxide in tetrahydro-furan by anhydrous potassium hydroxide, prepared in situ by addition of an equivalent of water to potassium naphthalene, was studied. The effect of time of polymerization, degree of conversion, and monomer and catalyst concentration on the molecular weights was studied. The system was a living one with no chain transfer. The efficiency of the catalyst was low. The polymerization was faster than those previously reported using solid potassium hydroxide due to the high dispersion of the catalyst prepared in this manner. The rate of polymerization increased about threefold by addition of two equivalents of dimethylsulfoxide to the catalyst due to solvation effects.

ISSN:0022-233X    

DOI:10.1080/00222337008059518

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The mechanism of the catalyzed linear polyurethane formation in the presence of dibutyltin dilaurate, copper acetylacetonate, and similar catalysts was investigated. It was found that the central ion coordinates with the isocyanate group. The second reacting component may be coordinated by the organic substituent or ligand groups near the central ion. It was concluded that the catalytic mechanism would vary depending on such reaction conditions as temperature, solvent, and the nature of the ligands near the central ion.

ISSN:0022-233X    

DOI:10.1080/00222337008059519

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The influence of aluminum-containing Lewis acids, e.g., AlCl3, AlEtCl2, AlEt2Cl, AlEt3, and AliBu3, on polyisobutylene, isobutylene-isoprene copolymer (butyl rubber), and chlorinated butyl rubber has been investigated in nonpolar and polar solvents at various Lewis acid concentrations in the temperature range -10 to -78°C. Polyisobutylene does not degrade even under the most aggressive conditions employed (AlEtCl2, -10°C). Butyl rubber degrades rapidly in the presence of AlEtCl2in the range -10 to -50°C. In contrast, no degradation occurs with the milder Lewis acid AlEt2Cl; however, in conjunction with small amounts of a suitable Bronsted acid (i.e., HCl) immediate and extensive degradation takes place with AlEt2Cl as well. Chlorobutyl rubber severely and very rapidly degrades in the presence of AlCl3and AlEtCl2. With the less acidic AlEt2Cl and AlEt3, molecular weight breakdown can be prevented only when employing milder conditions, i.e., at low Lewis acid concentrations in nonpolar solvents at lowest temperatures. A comprehensive mechanism involving carbonium ions of these degradation processes is proposed.

ISSN:0022-233X    

DOI:10.1080/00222337008059520

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

A sample of styrene-butadiene copolymer was fractionated by successive precipitation (one-direction fractionation) in cyclohexane/isooctane and benzene/methyl ethyl ketone systems. The chemical composition and molecular weight distributions of the sample were constructed from the fractionation data. The results obtained in both systems were nearly identical for the chemical composition distribution, but were different for the molecular weight distribution. The same sample was fractionated by cross fractionation using both solvent/nonsolvent systems. Comparing the results of cross fractionation with the results of one-direction fractionation, the first gave broader molecular weight and chemical composition distribution curves than the second. However, only cross fractionation showed that the chemical composition distribution curve has a long tail not only at the right side but also at the left side of the distribution maximum.

ISSN:0022-233X    

DOI:10.1080/00222337008059521

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The mass spectral characteristics of pivalolactone and its polymer have been determined. The monomeric lactone (MW 100) shows no molecular ion peak but does show peaks at 70 and 42 m/e associated with the loss of formaldehyde and then carbon monoxide and at 56 and 41 associated with the loss of isobutene and carbon dioxide. Only weak peaks, corresponding to the presence of traces of oligomers, are observed above m/e 71. The polymer, at volatilization temperatures of 250-350°C, gives fragments of up to 1242 m/e with a pattern recurring over intervals of 100 m/e units. The principal peaks occur at X42, X70, X83, and X01 m/e. Above 301, the X42 and X70 peaks are observable up to X = 12. The X70 fragment is assigned an acylium isobutyrate radical ion structure and the X42 fragment is assigned an isobutyl radical ion structure. The degradation products are accounted for as being formed from volatilized cyclic oligomers.

ISSN:0022-233X    

DOI:10.1080/00222337008059522

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Results of application of seven well-known bond energy/group contribution methods to the experimental data on heats of formation of 70 alkanes, including a few polymers, are reported. The earlier claims of accuracy of many of these schemes become untenable with the emergence of new data on nonanes and polymers, calling for more parameters to cope with the steric interaction energy in higher branched alkanes. A new general bond energy scheme is developed with low standard error of ±0.28 kcal/mole which is close to the experimental uncertainty. Heats of formation of some polyolefin structures are predicted for the experimental verification in the future. The energy terms of the new scheme are transferable to other non-hydrocarbon organic compounds for which a general scheme is under way.

ISSN:0022-233X    

DOI:10.1080/00222337008059523

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The copolymerization reactivity ratios designated as ri= kii/kijare characteristic of thermodynamic conditions, such as temperature, pressure, and concentration, in which the temperature dependence has been demonstrated by kinetic procedures [14]. It is noted that in radical copolymerization the simple product of the reactivity ratios, e.g., r1, r2generally tends to move toward unity with increasing temperature [2] and that for ionic copolymerization it is usually close to unity [5]. Such an inclination, however, involves some ambiguity in evaluating all the reported data [6] concerning the polymerization conditions.

ISSN:0022-233X    

DOI:10.1080/00222337008059524

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor