Glass transition temperatures have been studied for the random and block copolymers of styrene and cyclododecyl acrylate. The random copolymers showed a single glass transition temperature, which provided a concave glass transition temperature-composition curve. This concave relationship was fairly well represented by the modified Gibbs-Dimarzio equation of Uematsu and Honda, which includes the influence of the specific character of cyclododecyl acrylate as a monomeric unit. Each of the block copolymers as well as the blends of their component homopolymers showed two separated glass transition temperatures corresponding to the respective ones of poly(cyclododecyl acrylate) and polystyrene; these were independent of the total composition, owing to the incompatibility of the components.

A carbon(0)-bridged Pt2Ag2 cluster was synthesized from the reaction of a cyclometalated pincer carbodiphosphorane platinum complex with AgOTf, by forming Pt­(II)←C(0)→Ag­(I) dative bonds along with Pt­(II)–Ag­(I) and Ag­(I)–Ag­(I) metal–metal interactions. X-ray diffraction analysis reveals that the cluster adopts an antiparallel sandwich structure with a ladder-shaped PtC/AgAg/CPt core. The coordination plane of the platinum unit is highly distorted due to the in-plane steric repulsion between the PEt3 ligand on the platinum and the nearest proton on each of the two cyclometalated phenyl rings in the pincer carbodiphosphorane framework. The cluster is very labile and displays different reactivity patterns toward trivalent phosphorus ligands. In the reaction with bulky PPh3, a dinuclear complex was formed because of coordination of PPh3 to the silver atom upon cleavage of the tetranuclear core. In contrast, replacement of the PEt3 on the platinum center by P­(OPh)3, which is sterically less demanding, led to a dinuclear complex where the eliminated PEt3 ligand recoordinated to the silver atom.

synopsisThe anionic polymerization of t,hree monomers, 2-isopropenyl-4,5-dimethyloxazole(I), ~~p~~p~~_ y l t h i a z o l e~7 I~.~~s o p r~r o p~u~~p r i~~~~7 I I S ; . . w~~ -T h emonomers produced red-colored living polymers on addition of sodium naphthalene or living a -m e t h~~~3 . r e n~t € t~~e p BS BR iiiiitiak. It wasd39efved that a considerable amount of monomer remained in the respective living polymer-monomer system, indicating that an equilibrium between the polymer and the monomer existed as in the case of a-methylstyrene. At lower temperatures, the conversion of the monomer to the polymer i n c r d . The equilibrium monomer concentrations [Me] were determined a t different temperatures, and the heats ( A H ) and the entropies (AS') of polymerization were obtained byplottingln(l/[M.]) against 1/Tas A H = -9.4, -6.8, and -6.2 kcal/mole, AS" = -22.9, -16.5, and -16.6, eu for I, 11, and 111, respectively.

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