Sylvie Boileau

Crosslinking of polyether networks by hydrosilylation and related side reactions

Abstract The synthesis of a well defined poly(ethylene oxide) network is described. This was achieved by performing hydrosilylation of α,ω-diallyl PEO with 2,4,6,8-tetramethyltetrahydrocyclosiloxane (D 4 H). The influence of several factors, including the nature of the catalyst, temperature, (SiH)/(double bond) ratio and traces of water, on the hydrosilylation reaction is described. Side reactions were studied by 1 H and 29 Si n.m.r.

Soluble supramolecular polymers based on urea compounds

N,N′-Dialkylureas, which form intermolecular hydrogen bonds, are interesting precursors in the field of supramolecular chemistry. Particularly, N,N′-di(2-ethylhexyl)urea, which is soluble in nonpolar solvents, was shown by viscosimetry and FTIR spectroscopy to be associated in heptane at concentrations higher than 10 g l−1. The interactions involved are strongly reinforced by the cooperative association of two urea groups in the case of bis-ureas prepared from 2,4-toluene diisocyanate.

Reaction of functionalised thiols with oligoisobutenes via free-radical addition.: Some new routes to thermoplastic crosslinkable polymers

Abstract The functionalisation of vinylidene (isopropenyl) terminated oligoisobutenes (polyisobutenes; PIB) with several thiols has been realised in the presence of free-radical generators. Oxygen (air) is a significant accelerator for this reaction and in some cases, alone, is sufficient to cause the reaction to occur. Free-radicals were generated from peroxydicarbonates, AIBN or UV irradiation. The reaction is of an anti-Markovnikov type with the RS-function adding to the vinylidene CH2 group selectively in the presence of more substituted olefin groups in commercial PIB. A variety of thiols has been investigated and the synthesis of elastomeric polymers resulting from the hydrolysis and condensation of a trialkoxysilane coupled to PIB via a sulphide link has been demonstrated. The synthesis of comb-like polymers made by the addition of PIB to poly(mercaptopropyl methylsiloxane) has been achieved in a way to leave some non-reacted thiol functions available for crosslinking. A perfluoroalkyl thiol modified PIB shows a significant reduction in surface tension compared to the starting PIB polymer.

Novel polymer systems with very bulky organosilicon side chain substituents

Abstract Synthetic methods leading to novel polysiloxanes and polystyrene copolymers are described. Both types of polymer could be modified by incorporation of the highly sterically demanding tris(trimethylsilyl)methyl substituent (Me3Si)3C. The modification increases the rigidity of polymers as shown by d.s.c. analyses. The effect is especially dramatic in the case of silyl substituted polysiloxane copolymer. In that case the steric bulk of the tris(trimethylsilyl)methyl group renders 8% of Si-H bonds in poly(methylhydrosiloxane) (PMHS) unreactive towards the hydrosilylation process. The Si-H bonds of the resultant copolymer can be utilised in crosslinking of the linear polysiloxane.

Modification of polysiloxanes by free-radical addition of pyridylthiols to the vinyl groups of the polymer

Abstract Polysiloxanes containing pyridyl groups were prepared by thiol-ene addition to vinyl side groups of polysiloxanes. Apart from polymethylvinylsiloxane, poly(methylvinylsiloxane-co-dimethylsiloxane)s synthesized by three different methods were used: (1) equilibrium copolymerization of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V4) with hexamethylcyclotrisiloxane (D3); (2) kinetically controlled homopolymerization of 1-vinyl-1,3,3,5,5-pentamethylcyclotrisiloxane; and (3) kinetically controlled copolymerization of V4 and D3, which permitted us to obtain siloxane copolymers with different arrangements of the pyridyl groups along the chain. Addition of 2-(4-pyridyl)ethanethiol (PET) to the vinyl groups of these polymers proceeded with high yields, leading preferentially to β-addition products. The addition of 4-pyridylthiol (PT) proceeded much less readily. Polymers were characterized by FT-IR, 1H and 13C NMR, and by thermal analytical methods.

Silicon Based Polymers

Silicon Based Polymers presents highlights in advanced research and technological innovations using macromolecular organosilicon compounds and systems, as presented in the 2007 ISPO congress. Silicon-containing materials and polymers are used all over the world and in a variety of industries, domestic products and high technology applications. Among them, silicones are certainly the most well–known, however there are still new properties discovered and preparative processes developed all the time, therefore adding to their potential. Less known, but in preparation for the future, are other silicon containing-polymers which are now close to maturity and in fact some are already available like polysilsesquioxanes and polysilanes. All these silicon based materials can adopt very different structures like chains, dendrimers, hyperbranched and networks, physical and chemical gels.

Anionic Ring-opening Polymerization: Epoxides and Episulfides

Extensive studies of the mechanism and kinetics of the anionic polymerization of epoxides and episulfides have been reported during the last few decades, and they were reviewed quite recently by several authors.1–5 Most of the experiments were carried out with ethylene oxide (oxirane) and propylene sulfide (2-methylthiirane) because the living character of the polymerization of these two monomers, under specific conditions, has been well established;6, 7 propylene oxide (2-methyloxirane) polymerizes anionically with transfer to monomer, and poly(ethylene sulfide) is insoluble. In this chapter, the kinetics and mechanisms of the ring-opening reactions of epoxides and episulfides with nucleophilic initiators, as well as with the living ends during propagation, will be presented.

Metal-Free Activation in the Anionic Ring-Opening Polymerization of Cyclopropane Derivatives

The successful activation observed when using Bu(t) P(4) phosphazene base and thiophenol or bisthiols for the anionic ring opening polymerization (ROP) of di-n-propyl cyclopropane-1,1-dicarboxylate is described. Well-defined monofunctional or difunctional polymers with a very narrow molecular weight distribution were obtained through a living process. Quantitative end-capping of the propagating malonate carbanion was accessible by using either an electrophilic reagent such as allyl bromide or a strong acid such as HCl. Kinetics studies demonstrated a much higher reactivity compared to the conventional route using alkali metal thiophenolates.

Self-assembly of amphiphilic liquid crystal polymers obtained from a cyclopropane-1,1-dicarboxylate bearing a cholesteryl mesogen.

We study the self-assembly of a new family of amphiphilic liquid crystal (LC) copolymers synthesized by the anionic ring-opening polymerization of a new cholesterol-based LC monomer, 4-(cholesteryl)butyl ethyl cyclopropane-1,1-dicarboxylate. Using the t-BuP(4) phosphazene base and thiophenol or a poly(ethylene glycol) (PEG) functionalized with thiol group to generate in situ the initiator during the polymerization, LC homopolymer and amphiphilic copolymers with narrow molecular weight distributions were obtained. The self-assemblies of the LC monomer, homopolymer, and block copolymers in bulk and in solution were studied by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and transmission electron microscopy (TEM). All polymers exhibit in bulk an interdigitated smectic A (SmA(d)) phase with a lamellar period of 4.6 nm. The amphiphilic copolymers self-organize in solution into vesicles with wavy membrane and nanoribbons with twisted and folded structures, depending on concentration and size of LC hydrophobic block. These new morphologies will help the comprehension of the fascinating organization of thermotropic mesophase in lyotropic structures.

Liquid crystalline side-chain polymers. 1. Polysiloxanes with a carbonate group in the spacer

Abstract A series of new allyl and vinyl carbonates has been prepared by the reaction of allyl and vinyl chloroformates with 4-hydroxyphenyl esters of p -substituted benzoic acid, under phase-transfer catalysis conditions. These compounds, which exhibit nematic phases, have been bound onto a polysiloxane backbone by hydrosilylation. The side-chain polymers have been examined by 1 H and 13 C n.m.r. spectroscopy, g.p.c., differential scanning calorimetry and optical polarizing microscopy.