Free radical polymerization, synthesis functional polymers

Relatively few simple pyrimidine monomers have been incorporated into heterocyclic polymers (70MI11100). By far the greatest efforts with this ring system have involved polymerizable derivatives of nucleic acid bases and related compounds (81MH1102). The majority of this work has involved the synthesis and free radical polymerization of suitable vinyl- and acrylic-functional monomers, e.g. (134)-(136), although epoxy and other derivatives have also been studied. A number of the polymers exhibit base-paired complex formation with natural nucleic acid polymers or synthetic analogues, have found use in... 

Controlled free-radical polymerization methods, like atom-transfer radical polymerization (ATRP), can yield polymer chains that have a very narrow molecular-weight distribution and allow the synthesis of block copolymers. In a collaboration between Matyjaszewski and DeSimone (Xia et al., 1999), ATRP was performed in C02 for the first time. PFOMA-/)-PMMA, PFOMA-fr-PDMAEMA [DMAEMA = 2-(dimethylamino)ethyl methacrylate], and PMMA-/)-PFOA-/)-PM M A copolymers were synthesized in C02 using Cu(0), CuCl, a functionalized bipyridine ligand, and an alkyl halide initiator. The ATRP method was also conducted as a dispersion polymerization of MMA in C02 with PFOA as the stabilizer, generating a kine-... 

Besides some particular cases such as ozonolysis2,3) or ring-opening polymerization of ketene-acetal type monomers4), the hydroxytelechelic polymers can be synthesized also by anionic polymerization. This process leads to polymers with smaller polydispersity and to a theoretical functionality of two free-radical polymerizations are easier to carry out, cheaper and, therefore, of industrial importance. Several reviews deal with the synthesis of functionally terminated polymers s>6 7, while this paper concerns only radical processes leading to hydroxytelechelic polymers. 

There are in general two ways to synthesize side chain polymers, polymerization of peptide-functional monomers or introduction of the peptide moiety afterwards, by grafting. The latter technique is based on the synthesis of polymers containing some form of functionality in the side chain, normally an activated ester moiety, which can further react with a peptide. The most commonly used method for the polymerization of monomers containing active esters is free radical polymerization. In particular many activated acrylate esters have been polymerized in this manner [12] (Table 1) for use in a wide variety of applications, from the preparation of polymer drug conjugates [13,14] to supports for solid phase peptide synthesis [15,16]. 

Free-radical polymerization is an important process for the synthesis of polymers because free radicals are compatible with a wide variety of functional groups that are not compatible with ionic and metal-catalyzed polymerization. Therefore, free-radical polymerization is the most widely used method to produce polymers in industry. 

Graft copolymers were prepared by both classical strategies, that is, from enzymatically obtained macromonomers by subsequent chemical polymerization and by enzymatic grafting from hydroxyl functional polymers. Kalra et al. studied the synthesis of PPDL graft copolymers from macromonomers, which were obtained by the enzymatic ROP of pentadecalactone (PDL) from hydroxyethyl methacrylate (HEMA) and polyethylene glycol) methacrylate (PEGMA) [40]. Subsequently graft copolymers were obtained by free radical polymerization of the macromonomers. A similar approach was published by Srivastava for the HEMA-initiated enzymatic ROP of CL and subsequent free radical polymerization [41]. 

Among the carboxylic acid and anhydride functional monomers that have been employed in the synthesis of these thickener polymers are acrylic acid, methacrylic acid, itaconic acid, citraconic acid, maleic acid, fumaric acid, crotonic acid, maleic anhydride, and citraconic anhydride. The copolymers containing maleic and citraconic anhydride monomers are either hydrolyzed or partially esterified to obtain the required carboxyl functionality. Among these carboxylic monomers, maleic anhydride and particularly methacrylic acid are most frequently favored. Carboxylic homopolymers, where they can be formed, might be considered the simplest examples of ASTs were it not for the fact that they are not copolymers as defined, and some are water soluble in their un-ionized states. Examples of carboxylic homopolymers are the un-ionized free-radical-polymerized atactic forms of polyacrylic acid (i) and polymethacrylic acid (2), which are both readily soluble in water. 

Since the mid-1980s significant progress has been made with respect to the precision of polymer synthesis ranging from free-radical polymerization to advanced olefin polymerization and biotechnology. Novel structural and functional polymers are now at hand and offer new opportunities for improving adhesive formulations. Modern polymers can be tailored to offer problem solutions and properties on demand. This includes molecular design in conjunction with con-... 

This application of DEC chromophores requires synthesis of asymmetrically functionalized chromophores as illustrated in Fig. 1. In this example, the hydroxyl terminated end of the chromophore is capable of condensation polymerization reactions while the acrylate functionality is capable of undergoing free radical polymerization. In Fig. 2, we illustrate schematically the stepwise synthesis of a highly crosslinked polymer matrix where both ends of the chromophore are coupled to polymer main chains. The first step in the scheme shown is accomplished by free radical polymerization yielding a soluble and processible polymer with flexible pendant chromophore groups. This polymer is spin cast into an optical quality film (0.5-1.5 micron thickness) and is heated near the glass transition temperature, poled and subsequently crosslinked by a thermal crosslinking reaction involving... 

CRP provides a versatile route for the preparation of (co) polymers with controlled molecular weight, narrow molecular weight distribution (i.e., Mw/Mn, or PDI < 1.5), designed architectures, and useful end-functionalities. Various methods for CRP have been developed however, the most successful techniques include ATRP, stable free radical polymerization, " and reversible addition fragmentation chain transfer (RAFT) polymerization. " " CRP techniques have been explored for the synthesis of gels " " and cross-linked nanoparticles of well-controlled polymers in the presence of cross-linkers. 

To be covalently linked to the particles, the stabilizer must carry a group able to participate in one of the key steps of the free radical polymerization process (initiation, propagation, termination, or transfer reactions). According to the reaction in which they are involved, the reactive surfactants are referred to as inisurf (initiation), surfmer (propagation) or transurf (transfer). In these particular cases, the surfactant not only plays a key role in the formation of the particles and the functionalization of their surface, but also becomes an actor in the synthesis of the polymer chains that will form the particles. 

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