The present work discusses first the homopolymerization of omega-allyl, omega-undecenyl or omega-vinylbenzyl polystyrene (PS) macromonomers in the presence of selected early or late transition metal catalysts. Homopolymerization degrees were found to depend on the type of catalyst, the terminal double bond, the polymerization temperature and the concentration of the various species. Higher molar masses were reached at low temperatures and low catalyst and cocatalyst concentrations. Best results were obtained with the constrained geometry catalyst (CGC)-Ti.The same PS macromonomers were copolymerized with ethylene in the presence of the VERSI-POL (TM) catalyst to design a new type of poly(ethylene) based graft copolymer. The macromonomer weight percent content decreases with increasing ethylene pressure whereas the molar mass of the copolymer increases with ethylene pressure. The PS macromonomer content as well as the molar mass of the copolymer can be still increased by using alpha,omega-difunctional PS macromonomers. The dilute solution and solid-state behavior of these copolymers were examined and compared to those of poly(ethylenes) prepared under the same conditions. Copyright (c) 2006 John Wiley & Sons, Ltd.

The major part of the present paper discusses the ability of well-defined omega-undecenyl polystyrene, polyisoprene or poly(styrene-block-isoprene) macromonomers to undergo coordination homopolymerization in the presence of selected titanium catalysts. Special emphasis is given to the influence of the nature of the catalyst, the polymerization temperature and the macromonomer molar mass and concentration on homopolymerization yield and average degree of homopolymerization (DPn). Titanium-based catalytic systems such as CpTiCl3/MAO and Cp*TiCl3/MAO only yielded dimers. The use of the homogeneous metallocene catalyst with constrained ligand geometry (CGC-Ti/MAO) having an open active site, significantly improved the degree of polymerization. increasing macromonomer molar mass, causes only a slight decrease of DPn whereas conversion increased moderately. The final section briefly discusses the copolymerization of omega-undecenyl polystyrene macromonomers with ethylene in the presence of Versipol (TM) catalysts.

This paper deals with the coordination homopolymerization of omega-undecenyl poly(styrene-block-isoprene) macromonomers. The synthesis of the macromonomers made use of an anionic living poly(styrene-block-isoprene) copolymer which is deactivated at low temperature by 11-bromo-1-undecene. The ability of these macromonomers to get involved in coordination homopolymerization in the presence of selected titanium catalysts was discussed. Special emphasis was given to the influence of polymerization temperature, macromonomer molar mass and concentration on the yield of homopolymerization and average degree of polymerization (DPn). in the presence of the CGC-Ti/MAO catalyst, macromonomer conversion, determined by SEC, was between 35 to 52 wt.-%, and DPn was between 5 to 14 depending upon the experimental conditions. However, as revealed by SEC/LS, the resulting comb-shaped polymers (PE-graft-(PI-block-PS), are characterized by sharp molar distributions. Increasing macromonomer molar mass, led to only a slight decrease Of DPn whereas conversion increased moderately. Other titanium catalysts such as CpTiCl3/MAO and Cp*TiCl3/MAO only caused macromonomer dimerization.

ω-Allyl, ω-undecenyl and α,ω-undecenyl polystyrene macromonomers, well defined in molar mass and functionality, were synthesized via anionic polymerization. Their coordination copolymerization with ethylene with a cationic α-diimine palladium catalyst [(ArN=C(Me)–C(Me)=NAr)Pd(CH2)3(COOMe)]+BAr4′−, (Ar=2,6-iPr2–C6H3 and Ar′=3,5-(CF3)2–C6H3) affords access to a new type of graft copolymers constituted of a polyethylene backbone and polystyrene grafts. It was shown that the environment of the terminal double bond of the PS macromonomers has a huge influence on the polymerization behavior. Indeed, an undecenyl end-group is more reactive than an allyl end-group. The copolymerization of ethylene with α,ω-undecenyl polystyrene macromonomers lead to cross-linking for long polymerization time (18h at 25°C). The influence of several parameters (polymerization temperature, ethylene pressure, concentration) on molar masses and macromonomer incorporation yield was also investigated. Macromonomers having the lowest molar masses were the most reactive. The molar mass of the copolymer increased with ethylene pressure. As expected with such a chain walking catalyst, the copolymers presented moderately branched to highly branched structures depending on the ethylene pressure, like for the homopolymerization of ethylene. Finally, rheological investigations of the copolymers showed that a few percentage of polystyrene incorporation can change drastically the mechanical properties of the materials.

Macromonomer based poly(ethylene oxide) (PEO) hydrogels were tested with respect to their ability to serve as a template for the survival and the growth of hepatocytes. Two systems were considered : either the surface of preexisting hydrogels, with controlled structural parameters, were seeded with isolated rat hepatocytes or the hepatocytes were dispersed in physiological medium containing the macromonomer/initiator and heated to 37degreesC. In the first case, cells were examined at given times after spreading over two days. The results were compared to those observed for the dispersion of fibroblasts onto a surface of the same type of hydrogels. The effects of the structure of the hydrogels and its chemical nature on the extent of hepatocyte attachment (or encapsulation) and the morphology were investigated.

The present work discusses the synthesis of well-defined comb-shaped polymers or graft copolymer structures based on coordination (co)polymerization of macromonomers. Polystyrene macromonomers with various polymerizable entities were synthesized first by induced deactivation reactions. The homopolymerization of these macromonomers in the presence of selected early or late transition metal catalysts was examined. Comb-shaped polymers could be obtained over a large range of DP values. The results were compared to those obtained by anionic homopolymerization. Some results on the copolymerization of these PS macromonomers with ethylene in the presence of VERSIPOL(TM) type catalysts were presented.

Macromonomers have been extensively used, as well defined building blocks for various macromolecular architectures via anionic, ROMP and free radical homo- or copolymerization of omega-allyl, omegaomega-undecenyl and omega-vinylbenzyl polystyrene (PS) macromonomers, in the presence of early or late transition metal catalysts. The influence of several parameters (type of catalytic system, nature of polymerizable end-group and molar mass of the macromonomer) on the homopolymerization was first investigated. Whereas omega-allyl or omega-undecenyl PS macromonomers were not very reactive in homopolymerization whatever the catalyst, omega-vinylbenzyl PS macromonomers gave interesting results with CpTiCl3/MAO and Cp*TiCl3/MAO. The copolymerization of these macromonomers with ethylene was also studied in the presence of the following palladium catalyst: [(ArN=C-(Me)-C(Me)=NAr)Pd(CH2)(3)(COOMe)]+BAr'(-)(4)(VERSI-POL(TM)) (Ar=2,6-iPr(2)-C6H3 and Ar' = 3,5-(CF3)(2)-C6H3). omega-vinylbenzene PS macromonomers could not be incorporated into poly(ethylene) chains. On the contrary, the incorporation of omega-allyl PS macromonomers was achieved. Moreover, for macromonomers containing an alkyl spacer between the allylic unit and the PS chain, the incorporation rate, the copolymerization yield and the molar masses of the copolymers were increased, giving access to a new type of graft copolymer structure.

Brookhart and Gibson have recently described the synthesis of new iron and cobalt complexes with pyridine bis(imine) ligands for the polymerisation of ethylene and propylene. In the present paper, the synthesis of new complexes modified with heteroatoms, based on the above-mentioned catalysts, is reported. Higher activities are observed. The influence of the polymerisation temperature on the catalytic activity has been investigated. The first example of the successful copolymerisation of ethylene and 1-hexene with these catalysts is also discussed. The (co)polymers have been characterized by high temperature C-13 NMR. To cite this article: R. Souane et at., C. R. Chimie 5 (2002) 43-48 (C) 2002 Academic des sciences / Editions scientifiques et medicales Elsevier SAS.

The present work compares the efficiency of different polymerization methods to design well-defined comb-shaped structures based on macromonomers. Anionic polymerization remains the method of choice and allows the control of polymerization degree of the main chain and the length of the grafts. The presence of an active chain end on the backbone enabled the synthesis of a new type of hyperbranched polymers by reaction with appropriate low molar multifunctional compounds. Free radical polymerization is less efficient for the controlled homopolymerization of macromonomers but less sensitive to the presence of impurities. It requires in most cases long fractionation procedures to access well defined comb-shaped fractions characterized by high molar masses. The controlled free radical polymerization constitutes an interesting alternative. The homopolymerization of macromonomers with late transition metal catalysts was also examined and comb-shaped polymers characterized by a syndiotactic backbone and atactic grafts could be obtained.

Polymacromonomers are viewed as a special class of well-characterized branched polymers with high density of arms and shape ranging from spherical to nonspherical, depending on the arm functionality and molecular mass. We synthesized a series of such model systems with polystyrene or poly(methyl methacrylate) backbone and varying functionality and/or molecular mass of polystyrene arms and investigated their structure and dynamics in nondilute solutions (well above the overlapping concentration c*) and in the melt. We found similarities in their soft ordering and dynamic response with other well-known model branched polymers such as multiarm stars, in that cooperative and selfdiffusion or arm relaxation and structural rearrangements control their dynamics in solution or in the melt; respectively. However, the present systems do not follow the scaling laws of stars as a consequence of their anisotropy and the larger interpenetration needed to observe the effect of ordering on the dynamic response. The use of blends consisting of different polymacromonomers essentially enhances the polydispersity, enabling the detection of the self-diffusion mode in analogy to the multiarm stars, as well as obtaining a wide range of effective intermediate molecular masses, depending on composition. The mixtures investigated were miscible at all times and exhibited a dynamics dominated by the response of the slower components. These polymers complement the generic physical picture of the dynamics of branched polymers toward the low arm molecular mass.

The present paper discusses the ability of macromonomers to undergo polymerization and copolymerization with acrylic and vinylic monomers. These macromonomers have been synthesized by classical deactivation reactions. Special interest was devoted to macromonomers fitted with polymerizable methylmethacrylate end-groups. The anionic homopolymerization of omega-methacryloyloxy-polystyrene macromonomers was studied in detail and the influence of the molar mass of the macromonomer on the apparent propagation constant was determined. The anionic homopolymerization of omega-methacryloyloxy poly(ethylene oxide) macro-monomers was arise examined. In both cases, lithium chloride has to be added in order to reach a better control of the reaction. The dilute solution properties of these polystyrene polymacromonomers have been studied. Some preliminary attempts to apply that anionic homopolymerization of macromonomers to the preparation of "dumbbell" and "palmtree" polymers were presented.