Block copolymers catalysis

Metallocene catalysis has been combined with ATRP for the synthesis of PE-fr-PMMA block copolymers [123]. PE end-functionalized with a primary hydroxyl group was prepared through the polymerization of ethylene in the presence of allyl alcohol and triethylaluminum using a zirconocene/MAO catalytic system. It has been proven that with this procedure the hydroxyl group can be selectively introduced into the PE chain end, due to the chain transfer by AlEt3, which occurs predominantly at the dormant end-... 

Chain Shuttling Catalysis and Olefin Block Copolymers (OBCs)... 

Keywords Catalyzed olefin polymerization, Chain shuttling catalysis, Chain transfer, Olefin block copolymers, Thermoplastic elastomers... 

Poly(l,4-naphthylenevinylenes) have been prepared by metathesis polymerization of benzobarrelenes [181,182] and the photoluminescence properties of homopolymers and block-copolymers have been studied in some detail [183]. PPV also has been prepared via ROMP of [2.2]paracyclophane-l,9-diene [184] and ROMP of a paracyclophene that contains a solubilizing leaving group [185]. The resulting polymer is converted to PPV upon acid catalysis at room temperature. ADMET of 2,5-dialkyl-l,4-divinylbenzenes using Mo or W catalysts has... 

Scheme 6.2 Asymmetric hydrogenation of unsaturated amino acid derivatives as a model reaction for micellar catalysis using amphiphilic block copolymers.

Application of amphiphilic block copolymers for nanoparticle formation has been developed by several research groups. R. Schrock et al. prepared nanoparticles in segregated block copolymers in the sohd state [39] A. Eisenberg et al. used ionomer block copolymers and prepared semiconductor particles (PdS, CdS) [40] M. Moller et al. studied gold colloidals in thin films of block copolymers [41]. M. Antonietti et al. studied noble metal nanoparticle stabilized in block copolymer micelles for the purpose of catalysis [36]. Initial studies were focused on the use of poly(styrene)-folock-poly(4-vinylpyridine) (PS-b-P4VP) copolymers prepared by anionic polymerization and its application for noble metal colloid formation and stabilization in solvents such as toluene, THF or cyclohexane (Fig. 6.4) [42]. 

Scheme 6.3 Amphiphilic poly(2-oxazoline) block copolymers bearing triphenylphosphine and bipyridine moieties respectively as polymeric macroligands for micellar catalysis.

As an extension of the perspective of micelle formation by amphiphihc block copolymers the following part will focus on two other types of polymers. The micellar structures that will discussed are (i) micelles and inverse micelles based on a hyperbranched polymers and (ii) polysoaps, that are copolymers composed of hy-drophihc and amphiphihc or hydrophobic monomers. Whereas the first class of polymers is stiU very new and only few examples exist of the synthesis and appH-cation of such stracture in catalysis, the synthesis and aggregation characteristics of polysoaps has already been intensively discussed in the hterature. 

The application of Nd catalysis to the preparation of block copolymers with BR and PS building blocks has not been successful to the present day. Studies aiming at this target have been described by Jenkins [173]. 

A truly living polymerization allows for the preparation of block copolymers without the formation of the respective homopolymers. Reports are available on experiments in which Nd catalysis was applied to synthesize both diene/diene as well as diene/non-diene block copolymers. 

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