Challenges in polypropylene by chemical modification

Radical reactions of i-PP are a well known technical process for the chemical degradation to increase the flowability of the i-PP melt. By decreasing the temperature and increasing the life time of the PP-radicals, a process to synthesize long chain branched i-PP, was developed. The long chain branched-i-PP allows to introduce the i-PP in processing technologies as blow moulding film technology or foaming technology. The mechanism will be discussed. The radical grafting of Polypropylene (PP) becomes more important for the developing of PP-alloys with extended properties. Methylmethacrylate and styrene were polymerized and grafted in PP at low temperatures in solid state. Grafting and polymerizing in solid state means solving the monomers in the PP-powder directly from the reactor without contacting with oxygen (air). The reaction is started by the thermal decomposition of a peroxide. The reactivity of the primary radicals from the peroxide and the transfer reactions of the polymer radical of the PMMA or PS influences the amount of the grafted polymer. The solubility of the monomers and the peroxide in the amorphous i-PP-phase was measured. The grafting yield and the dispersity of the second polymer depends on the solubility and dispersity of peroxide and monomers in the PP-powder particles.     

Reductive PET-fragmentation-cyclization processes of bicyclo[n.3.0]alkanones: synthesis of angular quasi-triquinane and propellane systems

Bicyclo[3.3.0]octanone and bicyclo[4.3.0]nonanone derivatives with a cyclopropane unit in the α-position and an unsaturated side chain in the γ-position of the carbonyl group undergo fragmentation-cyclization processes leading to quasi-triquinane systems upon reductive photoinduced electron transfer (PET). For example, the new angular triquinane derivative 6 and the new propellane derivative 12 were synthesized in one step from these starting materials in moderate to good yields.     

Activation volume measurement for C[bond]H activation. Evidence for associative benzene substitution at a platinum(II) center

The reaction of the platinum(II) methyl cation [(N-N)Pt(CH(3))(solv)](+) (N-N = ArN[double bond]C(Me)C(Me)[double bond]NAr, Ar = 2,6-(CH(3))(2)C(6)H(3), solv = H(2)O (1a) or TFE = CF(3)CH(2)OH (1b)) with benzene in TFE/H(2)O solutions cleanly affords the platinum(II) phenyl cation [(N-N)Pt(C(6)H(5))(solv)](+) (2). High-pressure kinetic studies were performed to resolve the mechanism for the entrance of benzene into the coordination sphere. The pressure dependence of the overall second-order rate constant for the reaction resulted in Delta V(++) = -(14.3 +/- 0.6) cm(3) mol(-1). Since the overall second order rate constant k = K(eq)k(2), Delta V(++) = Delta V degrees (K(eq)) + Delta V(++)(k(2)). The thermodynamic parameters for the equilibrium constant between 1a and 1b, K(eq) = [1b][H(2)O]/[1a][TFE] = 8.4 x 10(-4) at 25 degrees C, were found to be Delta H degrees = 13.6 +/- 0.5 kJ mol(-1), Delta S degrees = -10.4 +/- 1.4 J K(-1) mol(-1), and Delta V degrees = -4.8 +/- 0.7 cm(3) mol(-1). Thus DeltaV(++)(k(2)) for the activation of benzene by the TFE solvento complex equals -9.5 +/- 1.3 cm(3) mol(-1). This significantly negative activation volume, along with the negative activation entropy for the coordination of benzene, clearly supports the operation of an associative mechanism.