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Supramolecular assemblies based on 4,4’-bipyridine as H-acceptor and a terthiophene carboxylic acid (3-TTAA) as H-donor were synthesized and characterized by FTIR and DSC. Their electropolymerization was successful in methylene chloride or in acetonitrile. The concept of using such supramolecular assemblies in electropolymerization opens the way to the facile synthesis of new π-conjugated polymers.

International audience; The synthesis and structural characterization of linear PolyC3 polymers containing trimethylene-1,1-dicarboxylate structural repeat units with C6F13 and C8F17 fluorinated side chains is described for the first time, and their properties were compared with the traditional polyvinyl structures thatdisplay the fluorinated chain on every second rather than on every third carbon alongside the backbone. Homopolymers as well as statistical and block copolymers with n-propyl and/or allyl trimethylene-1,1-dicarboxylate blocks have been obtained from PolyC3 precursors containing diallyl trimethylene-1,1-dicarboxylate units, by reacting C6F13−C2H4−SH and C8F17−C2H4−SH thiols with the allyl groups using a thiol−ene post- polymerization modification reaction. Solid-state properties have been investigated by differential scanning calorimetry for all of the (co)polymers and by small-angle X-ray scattering/wide-angle X-ray scattering for the C8F17 homopolymer at several temperatures. The structure of the homopolymer consistently shows a coexistence of two smectic phases at room temperature, which can be identified as SmB and SmC. This coexistence is assumed to arise from the fact that the distances between carboxylic oxygens bonded to the same carbon are very close to the ones between the neighboring carboxylic oxygens alongside the backbone, resulting in two possible ways of packing the pendant fluoroalkyl chains arranged in a hexatic order.

New bridged silsesquioxanes derived from isosorbide were synthesized, according to the sol–gel process, by acidic or basic hydrolysis and condensation of a bis-trimethoxysilyl precursor. The latter was prepared by thiol-ene photoaddition of 3-(trimethoxysilyl)-1-propane thiol on diallyl isosorbide ether synthesized by a phase-transfer-catalyzed reaction of allyl bromide with isosorbide. The structure of those hybrid networks prepared according to a sol–gel process was investigated by 29Si solid-state NMR and X-ray diffraction experiments. Acid hydrolysis leads to the formation of randomly branched structures while basic catalysis promotes the creation of clusters. The anisotropic character of the hybrid networks was evidenced by cross polarized optical light observations (birefringence), demonstrating an organization at the micrometric-scale. These hybrid networks derived from isosorbide showed a thermal stability up to 360 °C.

Recently, nitrogen–phosphorous hybrid organobases such as phosphazene bases (PBs), which possess a remarkably high basicity, have been extensively studied in organic synthesis. Their applications in the domain of anionic polymerization are reviewed. Those non-ionic superbases generate highly reactive anionic species according to two different pathways: firstly by deprotonation of weak acids in which the protonated phosphazene base forms the cation, and secondly by complexation of the lithium cation by the phosphazene base when organolithium compounds are used as initiators. They have been successfully used for the anionic ring-opening polymerization (AROP) of epoxides, cyclosiloxanes, cyclic esters, caprolactam, and very recently cyclopropane-1,1-dicarboxylates, as well as for the anionic polymerization of vinyl monomers such as methacrylates, acrylates, butadiene, and isoprene. Polymerizations with metal-free non-protonated phosphazenium counterions are also reviewed. In all cases, the rates of polymerization are much higher than those observed with metal cations, and similar to the values obtained with cryptated counterions. The use of protonated and non-protonated phosphazenium counterions leads generally to polymers with narrow molecular weight distributions, and well-controlled end groups. Advantages of PBs are discussed, and perspectives in the revisited domain of anionic activation applied to polymer chemistry are presented.

International audience; A synthetic method involving the in situ generation of an anionic initiator X− obtained by reaction of its conjugate acid precursor XH with ButP4 phosphazene base was tested as a possible way to easily and better control the end groups of polymers derived from the anionic ring-opening polymerization of cyclopropane-1,1-dicarboxylates. Several types of precursors were investigated, including thiols, alcohols, a carbazole, and a malonate. In all but one cases, a living polymerization mechanism could be observed, which was exploited to control the nature of the terminal end groups by reaction of the propagating malonate carbanion R−C(COOPr)2− with alkylating agents. It was also demonstrated that toluene was a much better solvent than the traditional one used in these reactions (THF) as a larger range of available temperatures was available despite an almost identical solvent influence on the polymerization. Exploitation of this feature provided access to higher degrees of polymerization than previously possible.

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The successful activation observed when using ButP4 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 carba- nion was accessible by using either an electro- philic reagent such as allyl bromide or a strong acid such as HCl. Kinetics studies demonstrated a much higher reactivity compared to the conven- tional route using alkali metal thiophenolates.

A series of novel oligomers with promesogenic groups on both termini were prepared by a hydrosilylation reac- tion between well-defined telechelic oligocarbosilazanes end-fitted with vinylsilane (SiVi) groups and promesogenic com- pounds containing one reactive hydrosilane (SiH) group. We investigated the correlations between the structure of the resulting mesogen end-capped oligomers and their phase behavior as examined by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM).

Combinations of fluorinated and silicone based elastomers were elaborated through the in situ synthesis of interpenetrating polymer networks (IPNs). The PDMS network was formed by dibutyltindilaurate catalyzed addition between the hydroxy end groups of α,ω-(3-hydroxypropyl)polydimethylsiloxane (PDMS) and a pluriisocyanate cross-linker. The poly(fluorinated acrylate) (polyAcRf6) network was obtained from free-radical copolymerization of a fluorinated acrylate with ethylene glycol dimethacrylate in the presence of dicyclohexyl peroxydicarbonate as the initiator. IPNs with different relative weight proportions of the fluorinated vs silicone partners were characterized by DMTA and DSC. Density refractive index and contact angle measurements reveal a satisfactory interpenetration degree of PDMS and polyAcRf6 networks. In addition, these materials present an unusual variation of density values and of the surface properties as a function of the relative weight composition.

In order to improve polyisobutene (PIB) mechanical properties, a PIB network is combined with a polystyrene (PS) one into an interpenetrating polymer network (IPN) architecture. PIB network is formed by alcohol addition between the hydroxyl end groups of a telechelic dihydroxy-polyisobutene and a pluri-isocyanate. PS network is synthesized by free-radical copolymerization of styrene with divinylbenzene. Thus, the optimal synthesis conditions are determined by FTIR spectroscopy and the kinetics of the alcohol–isocyanate addition is studied in detail. A short kinetic study of the PS network formation inside the PIB network is also carried out. The highest degree of interpenetration is obtained by forming the PIB network first. The corresponding transparent IPNs exhibit two mechanical relaxations corresponding to those of PS and PIB enriched phases. However, mechanical properties of PIB networks are tremendously improved by the presence of a PS network in such IPN architectures.

1 - Article; Oligoester-containing semiinterpenetrating polymer networks (semi-IPNs) can be effectively used as precursors for the generation of (meso)porous networks with tunable pore sizes. In a first step, novel poly(dl-lactide) (PLA)/poly(methyl methacrylate) (PMMA)-based semi-IPNs were prepared by varying two structural parameters, namely the cross-link density of PMMA subnetwork (initial MMA/dimethacrylate composition ranging from 99/1 to 90/10 mol %) and the cross-linker nature (bisphenol A dimethacrylate, diurethane dimethacrylate). The kinetics of the free-radical cross-linking process was monitored by real-time near-infrared spectroscopy. In a second step, the extraction of the un-cross-linked oligoester subchains from the semi-IPNs was investigated. The possibilities afforded by this straightforward and versatile route to (meso)porous polymeric materials were discussed, and the porosity of the resulting methacrylic networks was examined by scanning electron microscopy (SEM) and thermoporometry using differential scanning calorimetry (DSC). The dependence of pore sizes and pore size distributions on the cross-linker content and nature could be related to turbidity measurements of semi-IPN precursors and explained in terms of polymerpolymer miscibility through the evaluation of PLA/PMMA interaction parameters.

International audience; Supramolecular polymers are dynamic materials; consequently, their molar mass is concentration dependent. However, the present experimental results show that an efficient chain stopper (i.e., a monofunctional monomer) can be used to block the concentration dependence of the molar mass of a hydrogen-bonded supramolecular polymer, over a realistic concentration range. This fact was used to derive the molecular weight and radius of gyration of the stopped supramolecular chains (by light scattering) as well as the intrinsic viscosity. In a second step, the molecular weight of the bis-urea-based supramolecular polymer (EHUT) was determined in the absence of a chain stopper.

Porous polymeric materials offer a great versatility in most of the promising fields of applications. This article affords a critically selected overview of the recent synthetic strategies developed to design porous polymers and their potential applications in emerging areas of science and technology, such as analytical techniques, supported catalysis, controlled drug delivery, and so on. A large variety of macromolecular architectures can be employed in different template approaches: molecularly imprinted polymers, supramolecular assemblies, block copolymers, and polymer blends based on hyperbranched polymers are important precursors as specific template-oriented architectures for the creation of original porous polymers. Interpenetrating Polymer Networks represent a unique class of materials that have also been put forward for this purpose.

The oxidative coupling of telechelic [2-(propyn-1)oxyethyl]oxypropyl-terminated polydimethylsiloxanes, with the use of copper (I) chloride/TMEDA complex as the coupling catalyst, is described. The results of the studies on the influence of the reaction parameters (the catalyst concentration, the oxygen flow-rate and the nature of the solvent) are presented. UV curing of the polymers obtained in the course of the oxidative coupling is reported Copyright © 2003 Society of Chemical Industry

Telechelic, hydroxyalkyl terminated polydimethylsiloxanes were obtained under mild conditions via hydrosilylation of allyl alcohol or ethylene glycol monoallyl ether by oligomeric αω-hydride terminated polydimethylsiloxanes, with the use of a platinum catalyst. They were subsequently modified in a phase transfer catalyzed reaction by propargyl bromide, to give telechelic polysiloxanes terminated by acetylenic groups. The synthetic pathway is described and the characterization of the obtained products is presented.

Two different metallo-supramolecular amphiphilic block copolymers have been synthesized, using a hydrophilic poly(ethylene oxide) block connected through a bis-(2,2':6'2"-terpyridine-ruthenium) complex either to a hydrophobic polystyrene or to a poly(ethylene-co-butylene) block. These copolymers were used to prepare aqueous micelles. The morphological characterization of the metallo-supramolecular micelles was performed by dynamic light scattering and transmission electron microscopy. Besides individual micelles, larger structures were also observed by these two independent techniques. The larger structures were the result of aggregation of individual micelles. In addition, the influence of the ionic strength of the medium was investigated. Although the metallo-supramolecular copolymers do not contain charged blocks, the corresponding micelles behaved as polyelectrolyte-like micelles. This behaviour was attributed to the presence of NaCl ions, strongly associated to the poly(ethylene oxide) blocks. This was evidenced by transmission electron microscopy, that revealed the presence of the salt in the metallo-supramolecular micelles. (C) 2003 Society of Chemical Industry.

Symmetrical N,N'-disubstituted ureas have been synthesized and characterized. Among them, the branched dialkylureas prepared are highly soluble in organic media. Moreover, the solutions obtained are very viscous in heptane, if the branched alkyl groups are not too bulky (i.e. a methyl group on the alpha carbon, or an ethyl group on the beta carbon). Due to the strong, bifurcated hydrogen bonds between the urea moieties, linear supramolecular polymers are formed. The degree of association of these supramolecular polymers has been determined by FTIR spectroscopy.

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.

Three interpenetrating networks based on polymethylphenylsiloxane (PMPS) and polymethylmethacrylate (PMMA) with different compositions were prepared. They were investigated using differential scanning calorimetry (DSC) and high-resolution solid-state 13 C NMR techniques, in order to study the heterogeneous character of the domains involved in these materials at the nanoscopic scale. DSC observed broad glass transitions of the PMPS chains. 13 C cross-polarization (CP) experiments clearly showed that the aromatic PMPS carbons have a rate of CP which is composition dependent, indicating that PMPS and PMMA chains are interpenetrating at a very low spatial scale. These results were supported by T 1 ρ ( 1 H) and 13 C line width measurements as a function of temperature. Moreover, T 1 ρ ( 1 H) measurements indicated that PMMA chains are rather homogeneously distributed whereas PMPS chains belong either to interpenetrating domains or to PMPS-rich domains.

A metallo-supramol. ABC triblock copolymer contg. a bis(2,2':6',2''-terpyridine)ruthenium(II) complex as a supramol. connection between the constituting polystyrene-block-poly(2-vinylpyridine) diblock and poly(ethylene oxide) block (PS32-b-P2VP13-[Ru]-PEO70) was prepd. The copolymer was further utilized to prep. aq. micelles consisting of a PS core, a pH-sensitive P2VP shell, and a PEO corona. The micelles were characterized by a combination of dynamic light scattering, TEM, and at. force microscopy. Spherical micelles and a minor fraction of bigger aggregates were obsd. by these three independent techniques. The pH sensitivity of the P2VP shell was demonstrated and the reversibility of the metallo-supramol. complex was studied utilizing a strong competitive ligand. The bis(2,2':6',2''-terpyridine)ruthenium(II) connection was stable, and the integrity of the triblock copolymer was kept in the aq. environment even at extreme pH values. This complex is opened whenever a large excess of a strong competitive ligand was added, allowing the release of PEO coronal chains; the metal complex was then re-formed, even using a different metal ion. This last feature will be used in the near future as a tool to manipulate or to chem. modify nano-objects such as micelles. These micelles attractive for encapsulation and/or release of active species

Due to dimerization through hydrogen bonding of chain ends, benzoic acid terminated polydimethylsiloxane 1 forms a supramolecular polymer in low polarity solvents. Viscosity measurements in dichloromethane, carbon tetrachloride and hexane have been performed. In order to analyze the results, a covalent model 6 of the supramolecular polymer has been synthesized and its viscosimetric parameters (Mark-Houwink and Huggins constants) have been measured. It is experimentally shown that, in dilute solution, the viscosity of a supramolecular polymer can be satisfactorily evaluated if viscosimetric parameters of a suitable covalent model are known.

International audience; Linear aliphatic polyesters whose structure is made of short polyethylene glycol (PEG) segments connected along the chain by malonate units were synthesized from two PEG- containing macrolactones: 15,15-dimethyl-1,4,7,10,13-pentaoxacyclohexadecane-14, 16-dione (1) and 5,8,11,14,17-pentaoxaspiro[2,15]octadecane-4,18-dione (2). Anionic ring-opening polymerization conditions using either thiophenolates or a p-nitrophenolate as initiators yielded poly(ether-ester)s of low to moderate molecular weights, with broad molecular weight distributions. When the monomer also contains an activated cyclopro- pane unit of the cyclopropane-1,1-dicarboxylate type (such as in 2) and harsher polymer- ization conditions are used (higher temperatures and bulkier counterions), opening of the cyclopropyl ring can compete with the dilactone polymerization, providing access to cross- linked materials.

The synthesis of copolymers composed of dimethylsiloxane segments (DMS) of different lengths, regularly separated by one bisphenol A unit (BPA) is described. This was achieved by performing hydrosilylation of 2,2′-diallyl BPA with hydride terminated polydimethylsiloxanes in the presence of Pt(0) catalyst. The influence of several factors, including the control of the [Si–H]/[double bond] ratio and the protection of the –OH groups, on the molecular weight distribution of the polymers is described. Side reactions, such as the isomerization of the double bond and the O-silylation were studied by 1H and 29Si n.m.r. As expected, there is a strong influence of the DMS segment length and of the presence of H-bonding interactions on the thermal properties of the resulting polymers.

Three styrene derivatives bearing fluoroalkyl substituents in para or (meta/para) positions have been synthesized under phase-transfer-catalysis conditions. Homopolymers and copolymers with styrene have been prepared by free-radical polymerization. The monomer reactivity ratios of each monomer with styrene are determined by the Kelen–Tudo″s method. The results show that the fluoroalkyl substituent does not significantly affect the reactivity of the styrene double bond. Thermal and surface properties of the copolymers have been examined. Copolymers from the para-substituted styrene derivative show higher glass transition temperatures (Tg) than those obtained with the mixture of isomers. Low dispersive surface energies (11 < γ < 17 mNm-1) are determined from contact angle data measured with the Wilhelmy plate method. © 1999 Society of Chemical Industry

Two series of sequence random association chain liquid crystalline polymers have been synthesized by melt mixing a bispyridyl with dicarboxylic acids, which in their individual states are not liqui...

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.

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.

International audience; Benzoic acid terminated polydimethylsiloxanes (PDMS) have been synthesized by hydrosilylation of allyloxybenzylbenzoate with SiH terminated precursors followed by deprotection. These oligomers have been characterized by 1 H, 13 C and 29Si NMR, by FTIR and by SEC in tetrahydrofurane. Because of the flexibility and low polarity of the siloxane backbone, they are ideally suited to study the effect of hydrogen bonding on macromolecular properties.

Poly(1,1-dimethyl-1-silylethylene): -(SiMe 2 -CH 2 -CH 2 )- n was prepared by polycondensation of HSiMe2-CH2-CH2-SiHMe2 (A) with CH 2 =CH-SiMe 2 -CH 2 -CH 2 -SiMe 2 -CH=CH 2 (B) under suitable hydrosilylation conditions. Functional oligomers with either two SiH or two Si-CH=CH 2 end groups were obtained by using an excess of A or B respectively. These bifunctional oligomers were used as precursors for the preparation of well-defined networks by reaction with different tetrafunctional crosslinking agents such as D 4 H, D 4 Vi b) and tetravinylsilane (TVS). They were also used for the preparation of multiblock copolymers by reaction with dimethylsiloxane oligomers. Altemating copolymers were obtained from monomers containing siloxy or silanamine units. Thermal properties of these polymeric materials are presented.

Polydimethylsiloxanes with part of the siloxane units bearing an optically active sulfoxide group were synthesized. These copolymers had chiral sulfur centres connected to the siloxane chain by a dimethylene bridge. They were obtained mostly by the kinetically controlled anionic ring-opening polymerization of 1-(2-organothioethyl)1,3,3,5,5-pentamethylcyclotrisiloxanes, followed by stereoselective oxidation of prochiral groups to yield partially enantiomeric sulfoxide groups. Sulfoxides bearing cyclic monomers were also used. Polymers were characterized by spectroscopy and polarimetry. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 879–888, 1997

The kinetics of the anionic ring opening polymerization of hexaethylcyclotrisiloxane (D3Et) with the cryptate Li+/[211] as counterion have been studied by means of 13C NMR spectroscopy. The propagation reaction was found to be of first order in monomer as well as living end concentration. It proceeds by two decades slower than the corresponding reaction with hexamethylcyclotrisiloxane (D3Me) as monomer. The Li+/[211] system could be used to synthesize well defined polydiethylsiloxane (PDES) samples (Mw/Mn

The preparation of poly(dimethylsiloxane)s having part of the siloxane units substituted with a model organic thioether was investigated. The sulfur group was generated by the ene−thiol addition to...

Four fluorinated siloxane polymers labeled with fluorescent dyes were prepared by hydrosilylation of a mixture of allyl ethers with poly(methyl hydrogen siloxane). These comprised n-octyl allyl ether, 1H,1H,2H,-2H-perfluorooctyle allyl ether, and either 9-phenanthrylmethyl allyl ether or 9-anthrylmethyl ether. In addition a non-fluorinated polymer was prepared with the octyl allyl ether plus the phenanthryl ether. These yielded five polymers, mutually immiscible liquids labeled with chromophores appropriate for energy transfer studies. These experiments were carried out in 1,1,2-trichloro-1,2,2-trifluoroethane solution. Fluorescence decay profiles for the phenanthrene were all exponential, with lifetimes of 25 nsec for the allyl ether and 30 nsec for the polymer bound chromophore. Quenching was diffusion controlled, as expected; and the polymer-polymer reaction had a rate 5-fold slower than that between the phenanthryl and anthryl allyl ethers, independent of the fluorocarbon content of the polymer.

International audience; 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-BuP4 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 polymersexhibit in bulk an interdigitated smectic A (SmAd) 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.

International audience; A novel type of clickable polymers with a very high local density of allyl side groups was developed. These polymers were obtained by the anionic ring-opening (co)polymerization of diallyl cyclopropane- 1,1-dicarboxylate using as an initiating system a protic precursor whose acidebase reaction with the t-BuP4 phosphazene base generated the initiator in situ. The obtained polymers display geminated allyl groups on every third carbon alongside the macromolecular backbone. Homopolymers as well as block and statistical copolymers have been synthesized, with controlled molecular weights and narrow molecular weight distributions. The coupling of mercaptans with the allyl C]C double bonds has been investigated both thermally and photochemically, with the influence of the type of initiation on the efficiency of the polymer modification being discussed in comparison with other “clickable” systems. Further functionalization by several thiols was performed, leading to a range of functional poly(cyclopropane-1,1-dicarboxylate)s.

A novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes, in toluene or in the bulk, in the presence of the cryptand [211] or DMSO. Suitable conditions have been found in which monomodal distributions of molecular weights are observed for homopolymers of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V4) as well as for copolymers of V4 with D3 or D4.

A pyrene end-labelled poly(bisphenol AF-diethylene glycol carbonate) has been synthesized. Its molecular weight and end-group composition were determined through a combination of u.v. absorption and fluorescence decay measurements of the pyrene end-groups. Through gel permeation chromatography, several fractions were collected. For each fraction, the cyclization dynamics of the polymer in dilute solutions in acetone and toluene were investigated through studies of intramolecular fluorescent excimer formation. Values for 〈k1〉, the end-to-end cyclization rate constant, as well as for k−1 and kE were calculated.

Hydrosilylation of allyl carbamates by poly(methylhydrosiloxane) (PMHS) catalyzed by platinum- or rhodium-based complexes was investigated. About 10% of the carbamate molecules decompose during the hydrosilylation reaction through the cleavage of the carbamate bond. A redistribution process also takes place among the polysiloxane chains resulting in the formation of branched polymers but no crosslinking occurs. A mechanism for this side-reaction is proposed. © 1993 John Wiley & Sons, Inc.

A novel initiator, i.e. trimethylsilylmethyllithium has been successfully used for the ring opening polymerization of cyclosiloxanes in toluene, in the presence of the cryptand [211]. Suitable conditions have been found in which monomodal distributions of molecular weights of polysiloxanes are observed by GPC, even in the case of D4 and 1,3,5,7-tetramethyl-1,3,5,7-tetravinyl cyclotetra siloxane (D4Vi) polymerizations. Moreover, kinetics of propagation and of formation of cyclosiloxanes can be followed by 29Si or 13C NMR spectroscopy on living polymer solutions. The rate of propagation of hexaethylcyclotrisiloxane is 120 times lower than that of the corresponding dimethylated analog D3, under the same conditions.

Addition of perfluorooctyl iodide to the double bonds of vinyltrimethylsilane and 1,3-divinyltetramethyldisiloxane, followed by a reduction of the carbon-iodide bond, gives the corresponding C 8 F 17 CH 2 CH 2 Si moicty. Following this approach, |C 8 F 17 CH 2 CH 2 Si(Me)O| 4 . a precursor of highly fluorinated silicones. was conveniently prepared. without using hydrosilylation or Grignard reaction.

Fluorinated polyacrylates are highly hydrophobic and oleophobic. However, their poor mechanical properties prevent their development in many applications. Combination of a fluorinated polyacrylate network with a rigid cellulose acetate butyrate (CAB) network in an interpenetrating polymer network (IPN) architecture is an effective method for improving the mechanical properties of fluorinated polyacrylates. IPNs combining poly(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate) (polyAcRf6) with CAB were prepared according to an in situ polymerization/crosslinking synthesis. CAB was crosslinked by addition between unmodified hydroxyl groups and the isocyanate of a pluri-isocyanate crosslinker. The fluorinated network was obtained through free-radical copolymerization of 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl acrylate with poly(ethylene glycol dimethacrylate). The rates of formation of both networks were followed using Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) of IPNs show a single glass transition temperature and a single mechanical relaxation temperature, which are characteristic of a high degree of interpenetration between the partner networks. The mechanical properties of IPNs are greatly improved compared with those of the single fluorinated network. CAB/polyAcRf6 IPNs were prepared, and characterized using DSC and DMTA as well as contact angle measurements for their surface properties. As hoped, the mechanical properties of such materials are much improved compared with those of the fluorinated partner alone. Copyright © 2010 Society of Chemical Industry

13 C spin-lattice relaxation time measurements have been performed on cyclosiloxane cross-linked poly(ethylene oxide)s (PEO) in bulk at temperatures well above the T g . The introduction of cyclosiloxane cross-links does not induce a strong modification of the local dynamics of PEO segments, in contrast to results observed in urethane cross-linked PEOs. Moreover, in these networks, the local chain dynamics are satisfactorily described by considering a damped bond orientation diffusion process and a fast libration of limited extent of the internuclear CH vectors about their rest position

Procedures are described to synthesize and characterize linear and cyclic oligomers of poly(2,6-pyridinediyl sulfide) (PPyS). A two rotational state model was developed that gives a good account of the conformational statistics of this polymer. The relaxation behavior of PPyS in the vicinity of room temperature is strongly dependent on the crystallinity. ecular weight cyclic oligomers do not crystallize from the melt. Overlapping of Π orbitals of the pyridine ring with the p orbitals of the sulfur atoms does not seem to produce a noticeable increase in the conductive properties of PPyS at room temperature

Hydrosilylation of allyl carbonates by polymethylhydrosiloxane is a rather complex reaction. During the platinum catalyzed modification of polymethylhydrosiloxane with allyl phenyl carbonate, about 50% of the carbonate molecules decompose into CO2, propene and phenol. The released phenol reacts with the SiH functions of the polymer yielding Si-O-phenyl side groups. However the cleavage reaction can be avoided by using butenyl phenyl carbonate instead of allyl phenyl carbonate.

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.

The temperature-induced interchange between nonexcimeric and excimeric phosphorescence of poly[N-([vinyloxy]carbonyl)carbazole] (PFCZ) and poly[N-([allyloxy]carbonyl)carbazole] (PACZ) solid films was studied from 20 to 240K. Polystyrene doped with N-ethylcarbazole or N-carboethoxycarbazole was also studied.