Unexpected Radical Telomerisation of Vinylidene Fluoride with 2-Mercaptoethanol.

The radical telomerisation of vinylidene fluoride (VDF) with 2-mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed.

Well-defined syndiotactic polystyrene-b-atactic polystyrene stereoblock polymers.

New well-defined syndiotactic polystyrene-atactic polystyrene (sPS-b-aPS) stereoblock polymers were synthesized in a two-step process using a combination of "pseudo-living" Ziegler-Natta and atom transfer radical polymerizations. Under specific conditions, the one-pot termination with N-bromosuccinimide of syndioselective styrene polymerization catalyzed by Cp*Ti(CH(2) Ph)(3) /B(C(6) F(5) )(3) /Al(n-Oct)(3) (1:1:1) provided sPS-Br polymers almost perfectly (97%) end-capped with bromine atoms. These sPS-Br were used as macroinitiators in the ATRP of styrene affording sPS-b-aPS with a broad range of compositions. Characterizations by (1) H and (13) C NMR spectroscopy, HT-GPC and DSC confirmed the formation and identity of the new materials. Preliminary studies on the crystallization behavior under both isothermal and non-isothermal conditions showed that these sPS-b-aPS stereoblock polymers crystallize faster than the corresponding blends made of sPS and aPS with a similar composition; this effect is amplified at high contents (80%) of aPS in the stereoblock materials.

One-pot synthesis of lactide-styrene diblock copolymers via catalytic immortal ring-opening polymerization of lactide and nitroxide-mediated polymerization of styrene.

An efficient, practical, and industrially relevant procedure for the production of polymer materials, in which a part of the oil-derived polyolefins has been replaced by a renewable, biodegradable, and biocompatible poly(lactide) block, is presented. Binary catalytic systems combining innocuous metals (yttrium, zinc, magnesium, or calcium) and bifunctional alcohols (acting as transfer agents) were developed to promote the immortal ring-opening polymerization of lactide directly in styrene. Up to 20,000 equivalents of lactide were polymerized (metal catalyst loading of 50-100 ppm) in a controlled fashion in the presence of 10-100 equivalents of a double-headed transfer agent to give as many end-functionalized poly(lactide) macromolecules that can be used eventually as macroinitiators for the controlled nitroxide-mediated polymerization of styrene. The specific use of the sterically shielded complex [BDI-iPr]Zn-N(SiMe(3))(2) ([BDI-iPr]=bis(diketiminate) ligand) allowed the efficient, catalytic, and controlled production of poly(lactide)-block-poly(styrene) materials in a one-pot, solvent-free sequential procedure, with nearly 100% atom-efficiency.