Jacques Penelle

Synthesis and characterization of polyethylene-like polyurethanes derived from long-chain, aliphatic α,ω-diols

Abstract Long-chain aliphatic α,ω-diols containing up to 32 consecutive methylene groups were synthesized by several methods and characterized. 1,22-Docosanediol HO–(CH 2 ) 22 –OH and 1,32-dotriacontanediol HO–(CH 2 ) 32 –OH both exhibited a solid–solid phase transition before melting. The α,ω-diols HO–(CH 2 ) m –OH, where m =12, 22, or 32, were reacted in the melt with much shorter aliphatic α,ω-diisocyanates OCN–(CH 2 ) n –NCO, where n =4, 6, 8, or 12, producing a series of linear, aliphatic, and increasingly polyethylene-like m , n -polyurethanes. Characterization (by DSC, TGA, and SAXS) of the m , n -polyurethane series showed that when the aliphatic segments were increased, and the hydrogen-bonding densities thus decreased, the polymers displayed physical and thermal properties (for example, solubility and melting temperature) typical of polyethylene.

Experimental investigation on the reliability of routine SEC-MALLS for the determination of absolute molecular weights in the oligomeric range

Absolute number-average molecular weights were carefully measured for very-low to low molecular-weight poly(diisopropyl trimethylene-1,1-dicarboxylate) polymers that had been obtained from diisopropyl cyclopropane-2,2-dicarboxylate using a living anionic ring-opening polymerization technique (degree of polymerization in the range of 11-45 and polydispersity indices <1.13). Results obtained from four different analytical techniques, including end-group analysis (H-1 NMR), vapor pressure osmometry (WO), size-exclusion chromatography coupled to a multi-angle laser light-scattering detector (SEC-MALLS), and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-ToF), were compared and discussed. Although only crude estimates could be obtained by end-group analysis using H-1 NMR (experimental errors of up to 20%), (M) over bar (n) values estimated by SEC-MALLS were in perfect agreement with results obtained by VPO and MALDI-ToF. As the overall experimental protocol had been designed to prevent bias arising from some initial knowledge upon the exact molecular weights by the operator during the SEC-MALLS experiments, these results confirm a previous claim that SEC-MALLS is effective in measuring molecular weights in the oligomeric range

Reactive polymers incorporating silyl enol ether groups, 3. Incorporation of α,β-bis(siloxy)vinylene units into the backbone of vinyl polymers by free-radical (co)polymerization of 2,3-bis(trialkylsiloxy)butadienes†

2,3-Bis(trimethylsiloxy)butadiene (1) and 2,3-bis(tert-butyldimethylsiloxy)butadiene (2) have been homopolymerized and copolymerized with styrene (St) and methyl methacrylate (MMA) under free-radical conditions. Comparison of initial rates and molecular weights with polymerizations conducted under identical experimental conditions on monosubstituted analogs, 2-trimethysiloxybutadiene (3) and 2-(tert-butyldimethylsiloxy)butadiene (4), demonstrated that the second substituent does not decrease the polymerizability significantly despite the additional steric hindrance introduced in the monomer. Extensive H-1 and C-13 NMR characterization of the polymers demonstrated that the main incorporation mode is of the 1,4-type, allowing more than 95% of the butadienyl subunit to be incorporated in the main chain as an alpha,beta-bis(trialkylsiloxy)vinylene functional group. Monomer reactivity ratios r(1) and r(2) at 60 degrees C were determined from copolymer composition curves obtained at low conversions and are compared with values obtained for other 1,2-butadienyl systems.