Atom transfer polymerisation of methyl methacrylate can be effected using solid supported copper(i) pyridylmethanimine catalysts which facilitate easy removal and reuse of the catalyst.Controlled polymerisation of vinyl monomers, such as methacrylates, acrylates and styrene, is of continuing interest for the synthesis of polymers of specific composition and structure. 1 Controlled, or living, free-radical systems are attracting increasing attention as processes which are tolerant to protic species in the medium, e.g. from solvents, monomers, impurities, etc. Transition metal mediated living radical polymerisation, or atom transfer polymerisation, has been developed by Matyjaszewski 2-4 and Sawamoto, 5,6 utilising Cu(i)X/bipyiridines (X = Cl, Br) and Ru 2 Cl 2 (PPh 3 ) 3 , respectively. 7 In our laboratories we have been developing catalysts based on Cu(i)X and alkylpyridylmethanimine Schiff base ligands. [8][9][10][11][12] The attraction of these catalysts is that the Schiff base ligands are simple to synthesise and allow scope to vary the catalyst properties (e.g. redox potential, solubility) by varying the appropriate substituent groups.Typical [monomer] : [catalyst] ratios are 100 : 1 with stoichiometric amounts of initiator and catalyst, in order for acceptable rates of polymerisation. A potential solution to this problem is the use of supported catalysts. Inorganic supported catalysts, e.g. silica, have found widespread use in the polymerisation of olefins. 13 The extension of this approach to the use of functionalised inert poly(styrene) as supports for vanadium ethylene polymerisation catalysts has also been recently described. 14 This recent work prompts us to report our own work where we have been utilising supported catalysts for living radical polymerisation reactions; to the best of our knowledge this is the first example of the use of inert poly(styrene) supports for a non-co-ordination type polymerisation.We describe herein polymerisation of MMA mediated by Cu(i)Br supported Schiff base complexes (prepared from both primary amine functionalised silica gel and cross-linked poly(styrene) resins) via an atom transfer polymerisation process. In order to evaluate the potential of supported catalysts for atom transfer polymerisation, four different solid supports were tried in combination with CuBr. In the first two examples, the ligand was covalently attached to the solid support, either primary amino-functionalised silica gel (SiO 2 ) or aminofunctional cross-linked poly(styrene) beads (PS), Scheme 1. In the second and third examples, free ligand was used in conjunction with primary amine-functionalised and non-functionalised silica gel. The reactions were performed with 33 vol. % MMA in toluene solution with ethyl-2-bromoisobutyrate as the initiator.Addition of CuBr to ligated silica produces a dark brownorange free flowing powder, Scheme 1. † Atom transfer polymerisation of methyl methacrylate proceeds effectively at 90°C, reaching 70.4% conversion with a number average molecular mass, M n , of 15 500...

3-Aminopropyl-functionalized silica support (APSS) has been used as a solid support for the heterogeneous atom transfer polymerization of methyl methacrylate (MMA), to poly(methyl methacrylate) (PMMA), mediated by adsorbed RuCl2(PPh3)3 as catalyst. This system displays characteristics of a living radical polymerization as indicated by (i) an increase in the number-average molecular weight (M n) with conversion, (ii) relatively low polydispersity indexes (PDI), and (iii) linear first-order rate plots. When PMMA of M n = 20 000 g mol-1 was targeted, the reaction reached 91% conversion after 4 h with a measured M n = 21 500 g mol-1 and PDI = 1.49. It was found that polymerization of MMA mediated by RuCl2(PPh3)3 in the presence of APSS does not require the addition of an aluminum alkoxide (e.g., Al(OiPr)3) as an activating reagent. The rate of reaction is higher than for similar homogeneous reactions; however, the polydispersity indexes are also higher. The ruthenium content of polymers thus produced is typically approximately 0.1% w/w, corresponding to about 90% of the metal remaining adsorbed onto the surface of the support. This is thus an effective method of minimizing the metal content of the final polymer without postreaction purification. It is also shown that the supported catalyst can be reused for subsequent polymerization reactions. The polymers produced via this heterogeneous process can be subsequently used as macroinitiators to synthesize block copolymers and hence contain active halogen end groups.

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Solid-Supported Catalysts for Atom-Transfer Radical Cyclization of 2-Haloacetamides.-It is shown that copper(I) halide complexes of silica-supported ligands are efficient catalysts for the cyclization of activated and unactivated 2-haloacetamides. -(CLARK, ANDREW J.; FILIK, ROBERT P.; HADDLETON, DAVID M.; RADIGUE, ARNAUD; SANDERS, CHRISTO-PHER J.; THOMAS, GERARD H.; SMITH, MARK E.; J. Org. Chem. 64 (1999) 24, 8954-8957; Dep. Chem., Univ. Warwick, Coventry CV4 7AL, UK; EN)