Paul Rempp

Macromonomers: Synthesis, characterization and applications

The first part of this review critically examines the various attempts to prepare macromonomers: Anionic and cationic polymerization for synthesizing living polymers have been preferred whenever possible but two-step radical polymerizations making use of efficient transfer agents have also been applied.

Synthesis of ring-shaped macromolecules

Abstract Ring-shaped macromolecules have been synthesized by the reaction of a bifunctional “living” polystyrene with a stoichiometric amount of dibromo- p -xylene, at very low concentration. The reaction is carried out step by step, leading both to the expected cyclic polymer and to a “polycondensate”. Fractionatal precipitation and one-step fractionation lead to well defined macrocycles of known size.

Synthesis and characterization of polystyrene-poly(ethylene oxide) graft copolymers

Abstract Amphiphilic graft copolymers have been synthesized. The grafting reaction proceeds by anionic deactivation of a ‘living’ monofunctional poly(ethylene oxide) onto a partly chloromethylated polystyrene backbone. The copolymers are well-defined compounds (molecular weight of the backbone, number and length of the grafts are known), which exhibit narrow molecular weight distribution and are shown to be homogeneous in composition. The degree of grafting is high. Light scattering, vapour pressure osmometry, ultra-violet spectroscopy, nuclear magnetic resonance, differential refractometry and gel permeation chromatography were used for an accurate characterization of the structure of these copolymers.

Hetero-arm star copolymers with potentially ionogenic branches

Abstract Hetero-arm star copolymers—i.e. star polymers the cores of which carry branches of two different kinds—have been made by a three-step anionic process. The polystyrene (PS) precursor was made first, and used to initiate the polymerization of a small amount of divinylbenzene. The cores of the resulting star polymers still contain the active sites and can therefore be used to initiate the polymerization of another suitable monomer. tert.Butyl acrylate (t.BuA) was shown by Teyssie to polymerize anionically without transfer or termination, provided lithium chloride is present. An attempt was made to have poly(t.BuA) branches grow from the “living” cores of the PS star molecules. A detailed characterization of the resulting samples was performed, to establish whether these hetero-arm star copolymers exhibit the expected structure. The method can be considered quite reliable, and leads to star polymers with branches that are potentially ionogenic.

Cyclic macromolecules. Synthesis and characterization of ring-shaped polystyrenes

Abstract A method has been developed to synthesize cyclic polystyrene molecules, by reacting bifunctional “living” polystyrene with α,α′ dibromo- p -xylene. The ability of the method to yield cyclic polymers over a molecular weight range from 7000 to 250,000 has been thoroughly investigated and discussed. Characterization of the cyclic macromolecules with respect to linear homologues of the same molecular weight has been performed by means of viscometry. The effect of cyclization tends to decrease as the molecular weight increases.

Grafting and branching of polymers

This review summarizes the present state of investigations concerning synthesis of various types of model macromolecules. Emphasis was given to those methods which enable preparation of well characterized macromolecules, suited well enough for morphological and thermodynamic investigations in dilute solution, and to get information on the influence of heterocontact interactions and/or of enhanced segment density on the properties of the polymers considered. It can be seen that for such an aim, the anionic polymerization techniques which are versatile and well adapted to such problems, have yielded decisive progress. The main disadvantage of these methods is that the number of adequate monomers is rather limited. Other polymerization techniques do not involve active sites which retain their activity long enough to be of great interest for such synthesis.

Synthesis of polyethylene oxide macromers

SummaryAnionic “living” polymerization of oxirane was shown to be efficient for the synthesis of polyethylene oxide macromers. The double bond at chainend was introduced either upon initiation or upon deactivation. The macromers obtained were characterized carefully to establish quantitatively the presence of the end-standing double bond. The species are well defined and of narrow molecular weight distribution.

Kinetics of arm-first star polymers formation in a non-polar solvent

Star polymer formation by sequential anionic copolymerization of styrene and divinylbenzene in a non-polar solvent (benzene) was re-examined. Kinetic investigations established that the core formation is rather slow. Moreover, once the star molecules have reached their plateau molar mass, their cores still contain residual pendant unsaturations. This result arose from UV spectroscopic determinations, and was checked by sec-butyllithium addition to the star polymer solution. Fractionation experiments confirmed the rather narrow molar mass distribution in star polymer samples obtained by this arm-first process.

Synthesis and characterization of polyalkylmethacrylate macromonomers

SummaryThe synthesis of polyalkylmethacrylate macromonomers has been performed anionically by direct deactivation of the carbanionic sites with p-vinyl-or p-isopropenylbenzyl bromide. The characterization of the samples proved that the yields are close to quantitative, and that no side reactions are involved. The method also applies to hydroxyethylmethacrylate and to glycerylmethacrylate, provided the monomers are made aprotic by reversible silylation or acetalization.

Synthesis and characterization of multiblock copolymers containing poly(dimethyl siloxane) blocks

Abstract Multiblock copolymers of polystyrene and poly(dimethyl siloxane) were obtained by a hydrosilylation reaction between a,w dihydrogeno poly(dimethyl siloxane) and a,w -di(vinyl silane) polystyrene. Under well chosen experimental conditions the polycondensation is free of site reactions and the macromolecules formed are linear with up to 10 blocks, which corresponds to reaction of 90% of the functions initially present. The block copolymers obtained have been characterized by g.p.c. viscosimetry and light scattering.