Polymer structure modification functional monomer

Two different approaches can be used for the preparation of functionalized polymers Polymerization of functionalized monomers and chemical modification of preformed resins. Initially we selected this second approach, using polystyrene-divinylbenzene resins, as this allows to work with materials of well known structural characteristics. 

Owing to multi-functionahty, physical properties such as solubihty and the glass transition temperature and chemical functionahty the hyperbranched (meth) acrylates can be controlled by the chemical modification of the functional groups. The modifications of the chain architecture and chemical structure by SCV(C)P of inimers and functional monomers, which may lead to a facile, one-pot synthesis of novel functionahzed hyperbranched polymers, is another attractive feature of the process. The procedure can be regarded as a convenient approach toward the preparation of the chemically sensitive interfaces. 

Reactive polymers can be synthesized by either polymerizing or copolymerizing monomers containing the desired functional groups, or performing one or more modifications on a suitable polymer to introduce the essential functionality. Polymers produced directly by polymerization of functionalized monomers have well defined structures, but the physical and mechanical properties of the... 

Hawker et al. 2001 Hawker and Wooley 2005). Recent developments in living radical polymerization allow the preparation of structurally well-defined block copolymers with low polydispersity. These polymerization methods include atom transfer free radical polymerization (Coessens et al. 2001), nitroxide-mediated polymerization (Hawker et al. 2001), and reversible addition fragmentation chain transfer polymerization (Chiefari et al. 1998). In addition to their ease of use, these approaches are generally more tolerant of various functionalities than anionic polymerization. However, direct polymerization of functional monomers is still problematic because of changes in the polymerization parameters upon monomer modification. As an alternative, functionalities can be incorporated into well-defined polymer backbones after polymerization by coupling a side chain modifier with tethered reactive sites (Shenhar et al. 2004 Carroll et al. 2005 Malkoch et al. 2005). The modification step requires a clean (i.e., free from side products) and quantitative reaction so that each site has the desired chemical structures. Otherwise it affords poor reproducibility of performance between different batches. 

Another approach to the preparation of polymer-supported metal Lewis acids is based on polymerization of functional monomers. If synthesis of the functional monomer is not difficult, polymerization should afford structurally pure functional polymers, because the polymer formed requires no further complicated chemical modification. A variety of substituted styrene monomers are now commercially available styrene monomers with an appropriate ligand structure can be prepared from these. Several other interesting functional monomers such as glycidyl methacrylate, 2-hydr-oxyethyl methacrylate, and other acrylics have also been used extensively to prepare functional polymers. 

Synthetic polymers include macromolecules formed from monomers by chemical polymerization reactions. Synthetic polymers possess some significant advantages over natural polymers, such as high purity and better reproducibility. The properties of synthetic polymers, such as degradation rate, hydrophobicity and drug release rate, can be manipulated easily by structural modifications or formulation parameters. Synthetic polymers can be modified and functionalized easily and they allow production of tailor-made nanocarriers. These nanocarriers sustain the release of the encapsulated therapeutics over a period of hours to weeks in an adjustable manner. ... 

Chapter 5 by Ishihara and Fukazawa focuses on polymers obtained from 2-methacryloylo>yethyl phosphorylcholine (MPC) monomer. Indeed, the molecular design of MPC polymers with significant functions for biomedical and medical applications is summarized in detail. It is especially shown that some MPC polymers can provide artificial cell membrane-like structures at the surface as excellent interfaces between artificial systems and biological systems. In the clinical medicine field, MPC polymers have been used for surface modification of medical devices, including long-term implantable artificial organs to improve biocompatibilily. Thus some MPC polymers have been provided commercially for these applications. 

In this approach, functionalized monomers are employed to synthesize process-able ICPs. During the past few years, some progress has been made in the chemical modification of the parent ICP structures to obtain more soluble polymer de-... 

The second way involves direct copolymerization of functionalized monomers. Modification of monomers is a fundamentally different approach from modification of polymer in that modification of monomer makes feasible control of the molecular structures. Both diphenols and dihalide aryl sulfones can be modified to incorporate functional groups or new counterparts. 

There are certain similarities in the structures of synthetic and natural polymers such as nylon and protein, synthetic and natural rubbers, but sometimes the breadth of function is far greater in natural polymers. For example spider silk has the strength of Kevlar combined with greater stretch [17]. Several polymers may also be produced by modification of natural polymers or polymerization of monomers from renewable resources. 

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