Monomers surface grafting

Two general methods of improving polymer hemocompatibility are known (1) grafting of hydrophilic chains, and (2) the chemical attachment of an antiplatelet agent. In this respect, many hydrophilic and other monomers are grafted on solid polyurethane surfaces such as... 

The chain architecture and chemical structure could be modified by SCVCP leading to a facile, one-pot synthesis of surface-grafted branched polymers. The copolymerization gave an intermediate surface topography and film thickness between the polymer protrusions obtained from SCVP of an AB inimer and the polymer brushes obtained by ATRP of a conventional monomer. The difference in the Br content at the surface between hyperbranched, branched, and linear polymers was confirmed by XPS, suggesting the feasibility to control the surface chemical functionality. The principal result of the works is a demonstration of utility of the surface-initiated SCVP via ATRP to prepare surface-grafted hyperbranched and branched polymers with characteristic architecture and topography. 

During the last few years, new developments in polymer photochemistry have made it possible to graft various functional monomers onto surfaces of inert polymers like polyethylene, polypropylene and polyethyleneterephthalate. In the first attempts, initiator and monomer were transferred in vapor phase into a "UV Cure" irradiator containing the polymer sheet to be surface grafted. 

UV light in a second step. In later work reported by Tazuke, Kimura et al. (6-8) successful photograftings on the polymer surface of thin films (polyethylene, polypropylene and polystyrene) were achieved with various monomers. In this work, grafting was induced by UV irradiation through the film which was in contact with a solution containing initiator and monomer. The method is slow and - in addition to surface grafting - large amounts of homopolymer are formed. 

UV-induced surface grafting of a polymer sheet using vapor phase transfer of sensitizer and monomer from a volatile solution (9). 

UV-induced surface grafting of a polymer tape or a fiber bundle as substrate in a continuous operation with pretreatment of the substrate (presoaking) in a solution of sensitizer and monomer (10). The grafting takes place in a thin layer of solution on the surface of the moving substrate. 

Table 1. Monomers Used for Surface Graft Copolymerization onto Polyolefin Surfaces...

Tab. 8.5 Functional monomers used for surface-grafting of monolithic supports.

The mechanism and kinetics of RAFT-SIP were studied by Fukuda et al. [326]. Besides the expected linear increase of the molecular weight of the surface grafted polymer with the monomer conversion, they observed the appearance of a prominent low molar mass fraction which was attributed to a combination reaction of the propagating active chains. 

MIP films, applied to a QCM transducer, have been employed for chiral recognition of the R- and 5-propranolol enantiomers [107]. MIP films were prepared for that purpose by surface grafted photo-radical polymerization. First, a monolayer of 11-mercaptoundecanoic acid was self-assembled on a gold electrode of the quartz resonator. Then, a 2,2 -azobis(2-amidinopropane) hydrochloride initiator (AAPH), was attached to this monolayer. Subsequently, this surface-modified resonator was immersed in an ACN solution containing the MAA functional monomer, enantiomer template and trimethylolpropane trimethacrylate (TRIM) cross-linker. Next, the solution was irradiated with UV light for photopolymerization. The resulting MIP-coated resonator was used for enantioselective determination of the propranolol enantiomers under the batch [107] conditions and the FIA [107] conditions with an aqueous-ACN mixed solvent solution as the carrier. The MIP-QCM chemosensor was enantioselective to 5-propranolol at concentrations exceeding 0.38 mM [107]. 

The energy associated with UV light is in competence with the chemical bond energies associated with any two atoms [104]. Hence, UV radiation often has the potential for retention of the properties of monomers and polymers while the other surface grafting techniques, which use ionisation radiation, cause damage to the substrate polymer due to excessive degradation. 

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