We describe the synthesis, characterization and properties of various types of siloxane polymers containing diphenylsiloxane (P) as a component. The polymer types include di-and tri-block copolymers with dimethylsiloxane (M) as the second component, and random and statistical copolymers with dimethylsiloxane or methylphenylsiloxane (P/M) as the second component. Such copolymers combine siloxane units whose polymers have very different properties. The polydiphenylsiloxane chain is rigid and inflexible, and the polymer is a highly crystalline solid with a liquid crystalline or condis crystalline state and a very high melting (clearing) temperature. In contrast, the polydimethylsiloxane or polymethylphenylsiloxane chains are very flexible and the polymers have very low glass transition temperatures.Polymers of controlled molecular composition, size and architecture were prepared by anionic polymerization of the "cyclic trimers", using lithium-based initiators.The physical properties of the copolymers vary dramatically with composition and architecture. Two types of "random" copolymers can be prepared. In one type, siloxane units of a given type are randomly placed in the chain in groups of three, i.e., the minimum sequence length of a given siloxane type is three siloxane units. In the other type of random copolymer, individual siloxane units are randomly distributed so that the minimum sequence length is a single siloxane unit. The properties of the two types are quite different, showing that subtle changes in sequence distribution can have major effects on physical properties. At molar ratios near 1/1 and with molecular weights of -105 , the first type of "random" copolymer is an elastic solid with appreciable mechanical properties, whereas the latter type is a sticky gum.Diblock copolymer (P-M) with dimethylsiloxane as the major component are paste-like, whereas the triblock (P-M-P) and star-block copolymers of the same composition are tough elastomers. The block copolymers are molecular composites, in which the polydiphenylsiloxane component separates into crystalline microphases with very uniform fibrillar or lamellar morphologies, and with widths or thicknesses comparable to the length of the polydiphenylsiloxane block, i.e, typically of the order of 100 A.

SynopsisThe kinetic3 of the photopolymerization of styrene in bulk and in dilute systems in the presence of benzoin isobutyl ether as photoinitiator have been examined. The values of the intensity exponent, calculated at different temperatures or at different styrene concentrations, and the monomer exponent, calculated at various intensities, showed significant departure from those predicted by the ideal kinetic scheme, particularly at high intensity, at low temperature, or at low styrene concentrations. Low molecular weight polymer was the dominant product when high light intensity or low polymerization temperature was used. As the temperature was raised, however, or as the intensity was reduced, a high molecular weight polymer became progressively more important. Kinetic and molecular weight data suggest that at low temperature, high intensity, and/or at low monomer concentration, the benzoyl radical is the dominant initiating species; and the benzyl ether radical was consumed mainly in the termination step. At low intensity, high temperature and/or high monomer concentration, however, it appears that both benzoyl and benzyl ether radicals initiated polymerization.

Addition chlorination of cis‐1,4‐polybutadiene in the presence of acetic acid as a cosolvent resulted in the formation of head‐to‐head vinyl chloride–vinyl acetate copolymer. Chlorine analysis, IR, and NMR spectra of the chlorinated polybutadiene indicated that reaction was primarily double bond addition; there was little evidence for substitutive chlorination. Acetate was incorporated by nucleophilic participation of the acetic acid cosolvent. The extent of incorporation of the acetate group in the polymer chain was a function of the acetic acid concentration. Both the glass transition temperatures and the densities of the chloroacetylated polymers decreased as the degree of acetylation increased.