Synthesis comb-type polymers

The synthesis of comb-type polymers with randoni hydrophobe placement, via addition of the hydrophobes to the isocyanate functions of preformed polymer, is illustrated in Scheme III. This type of polymer geometry... 

Dai W, Zhu J, Shangguan A, Lang M (2009) Synthesis, characterization and degradability of the comb-type poly(4-hydroxyl-e-caprolactone-co-e-caprolactone)-g-poly(L-lactide). Eur Polym J 45 1659-1667... 

A synthetic pathway that appeared to be most convenient and promising for the synthesis of LC polymers was proposed and proved in Moscow State University in 19736,8 10) and involved the use of so called comb-like polymers containing long paraffinic fragments in each monomer unitl2,33) (Fig. 2). Macromolecules of comb-like polymers are constituted of two types of structural units — the main chains and the side chains. Their behaviour is mutually dependent as they are chemically linked and at the same time both parts are sufficiently independent because the side chains are long enough. 

Wall FT (1942) Statistical thermodynamics of mbber. J Chem Phys 10 132-134 Wall FT (1943) Statistical thermodynamics of mbber. III. J Chem Phys 11 527-530 Wall FT (1951) Statistical thermodynamics of mbber elasticity. J Chem Phys 19 1435-1439 Yan Q, Hoffman AS (1995) Synthesis of macroporous hydrogels with rapid swelling and deswelling properties for delivery of macromolecules. Polymer 36 887-889 Yoshida R, Uccida K, Kaneko Y, Sakai K, Kikuchi A, Sakurai Y, Okano T (1995) Comb-type grafted hydrogels with rapid deswelling response to temperature changes. Nature 374 240-242 Zerbi G (1999) Modem Polymer Spectroscopy. Wiley-VCH, Weinheim... 

The synthesis of polymers capable of entering into a chiral nematic phase initially proved difficult as many of the acrylate and methacrylate comb-branch polymers to which a cholesterol unit was attached as a side chain tended to give a smectic phase. This was overcome by either copolymerizing the cholesterol-containing monomers with another potential mesogenic monomer, or by synthesizing mesogens with a chiral unit in the tail moiety. Examples of both types are shown as structures VIII and IX. 

As a unique method of controlled/living radical polymerization, ATRP has had a tremendous impact on the synthesis of macromolecules with well-defined compositions, architectures, and functionalities, including star- and comb-like polymers as well as branched, hyperbranched, dendritic, network, cyclic type structures and so forth. 

The use of macromonomers in controlled living polymerization techniques, such as ionic or CRP, is at present the preferred synthesis strategy for the preparation of relatively well-defined graft copolymers. Macromonomers are oligomers fitted with polymerizable end-groups, mainly styrenic or (meth)acrylic, that can copolymerize with monomers to form comb-type graft copolymers with pendent preformed polymer chains. 

One of the primary thrusts in oligomeric research has been in developing oligomers as intermediates in preparative polymer chemistry. The chemistry of chain-ended functional oligomers is important to preparative polymer chemistry because of their use as macromonomers, telechelics and any other type of reactive oligomer. Macromonomers have been used as precursors for the synthesis of graft copolymers, comb-like polymers and networks. Telechelics have been used primarily to synthesize block copolymers," polymer networks and interpenetrating polymer networks. 

The problem of molecular weight distribution (MWD) and functionality type distribution (FTD) belongs by definition to an extensive problem of molecular heterogeneity of polymers. In the synthesis of a polymer with the requested properties, e.g. a telechelic polymer, one is always faced with different types of polydispersity the macromolecules can be of different length, they can have a different number of functional groups, i.e. be mono-, bifunctional, etc., they can be branched (star-, comb- or tree-like) and, finally, they can be cyclic. 

During the last years most efforts at preparing LCPs have focused on the use of rod-like mesogens. Only very recently has the synthesis of mesomorphic polymers with disclike units (see Fig. 1) been reported [29,30]. Likewise, combing main-chain/ side-chain polymers (see Fig. 1), comprising structural aspects of both types of LCPs, have only recently become known [31]. 

The CCT reaction has attained commercial utility as it is ideal for synthesizing low molecular weight polymers with terminal imsaturation. The resnltant macromonomers can be used as either chain transfer agents (useful for making block structures) or polymerizable monomers, useful in the synthesis of comb- and star-type molecules. The reaction is tolerant of many frmctionalities and of water, making it amenable to emulsion reactions. 

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