Macromolecular engineering

A chain-end-stereocontroUed polymerization of meso-lactide was also observed, the bulky achiral P-diiminate-zinc complex 7 [18b] leading to syndiotactic PLAs (CH2CI2, 0°C, Pr 0.76) and N-heterocyclic carbenes IMes leading to heterotactic PLAs (P, up to 0.83 at -40°C) [47bj. 

5) The different synthetic routes to symmetrically and dissymmetrically substituted l,4-dioxane-2,5-diones have been recently reviewed (see Ref [2d]). 

6) This selectivity is supported by the higher reactivity of glycolide versus lactide (roK-lO). 

Sn(Oct)2 as a catalyst, further developments have so far been limited by the poor availability of the crossed dimer 21 (obtained in two steps and 43% overall yield from glycolic acid and 2-bromopropionyl bromide) [53b, 54], 

Although the ROP of substituted l,4-dioxane-2,5-diones allows for the preparation of modified PLAs, its application is limited from a practical standpoint by the only moderate polymerizability of these monomers. Activated equivalents thereof would be highly desirable, and from this point of view O-carboxyanhy-drides (OCAs) appear very promising candidates [60]. Indeed, the organocatalytic 

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Malmstrom, E.E. and Hawker, C.J. Macromolecular engineering via living free-radical polymerizations, Macromol. Chem. Phys., 199, 923, 1998. 

Puskas, J.E., Antony, P., Paulo, C., Kwon, J., Kovar, M., Norton, P., and Altstadt, V. Macromolecular engineering via carbocationic polymerization Branched and hyperbranched stmctures, block copolymers and nanostructures, Macromol. Mater. Eng., 286, 565-582, 2001. 

Matyjaszewski, K. Macromolecular engineering From rational design through precise macromolecular synthesis and processing to targeted macroscopic material properties. Prog. Polym. Sci., 30, 858, 2005. 

Kennedy JP, Ivan B (1992) Designed polymers by carbocationic macromolecular engineering. Theory and practice. Hanser Publishers, Munchen, Germany... 

Matyjaszewski K, Gnanou Y, Leibler L (2007) Macromolecular engineering-precise synthesis, materials properties, applications. Wiley-VCH, Weinheim... 

The purpose of this review is to report on the recent developments in the macromolecular engineering of aliphatic polyesters. First, the possibilities offered by the living (co)polymerization of (di)lactones will be reviewed. The second part is devoted to the synthesis of block and graft copolymers, combining the living coordination ROP of (di)lactones with other living/controlled polymerization mechanisms of other cyclic and unsaturated comonomers. Finally, several examples of novel types of materials prepared by this macromolecular engineering will be presented. 

Macromolecular engineering is the ultimate goal of the polymer chemist when he has a monomer or a family of monomers at his disposal. Once each step of the polymerization process is carefully controlled, every molecular parameter of the polymer is predictable molecular weight, tacticity, molecular weight distribution, nature of the end groups, microstructure, and composition, and block... 

With the idea of extending the scope of the macromolecular engineering of aliphatic polyesters, the coordination-insertion ROP of lactones and dilactones has been combined with other polymerization processes. This section aims at reviewing the new synthetic routes developed during the last few years for building up novel (co)polymer structures based on aliphatic polyesters, at least partially. 

Matyjaszewski, G. Gnanou, Y. Leibler, L., editors. Macromolecular engineering. Volume 1 Synthetic technique. Wiley-VCH, Weinheim, 2007. 

Keywords Aliphatic polyester Biodegradable polymer Functionalized polymer Lactone Living polymerization Macromolecular engineering Ring-opening... 

Dubois P, Jerome R, Teyssie P (1989) Macromolecular engineering of polylactones and polylactides. I. End-functionalization of poly-e-caprolactone. Polym Bull 22 475 82... 

Kennedy, J. P. andB. Ivan, Designed Polymers by Carbocationic Macromolecular Engineering. Theory and Practice, Hanser, Munich, 1992. 

Gnanou, Y. and D. Taton, Macromolecular Engineering by Controlled/Living Polymerization, Chap. 14 in Handbook of Radical Polymerization, K. Matyjaszewski and T. P. Davis, eds., Wiley-Interscience, New York, 2002. 

W. Radke, Chromatography of polymers, in Macromolecular Engineering Structure-Property Correlation and Characterization Techniques, vol. 3, K. Matyjaszewski, Y. Gnanou, L. Leibler, eds., Wiley-VCH, Berlin, Germany, 2007 A.M. Striegel, J.J. Kirkland, W.W. Yau, D.D. Bly, Modem Size-Exclusion Liquid Chromatography, Wiley, Hoboken, New Jersey, 2009. 

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