Polymer latices surface modification

Seeded polymerization using a slight amount of monomer leads to the surface modification without changing particle size. The resulting particles are a kind of core-shell particles or, more exactly, core-skin particles (Fig. 12.2.4C). Seeded polymerization of sugar-units-containing styrene derivative on polystyrene seed particle was carried out to obtain latex particles covered with sugar units (17). A necessary condition for this is that the monomer is more hydrophilic than the seed polymer. If not, the monomer permeates into the seed particle and only a small fraction remains on the... 

His research interests include organic-inorganic nanocomposites, novel filler surface modifications, thermal stability enhancements, polymer latexes with functionalized surfaces, etc. He has authored more than 40 scientific publications, book chapters, and patents on these subjects. 

Surface imprinting of latex particles is an approach to use functional groups present on the surface of a polymer and fix their conformation by a surface modification with another polymer [84,85]. An attempt had been made to reduce the nonspecific binding by applying a hydrophilic coating after the MIP preparation [86]. 

Interest continues in the binding of heparin to polymers in an attempt to produce non-thrombogenic surfaces. This has been the aim in the use of glutaralde-hyde-protein complexes as coatings for latex rubber and polyurethanes. Glutaraldehyde has also been used to bind antibodies to partially hydrolysed polyamide surfaces for enzyme-linked radioassay techniques. One of the few examples of direct polymerization (as opposed to surface modification) in an attempt to produce polymers having improved compatibility involves the use of 2-methacryloyloxyethylphosphoryl choline in the formation of homopolymers and copolymers with methyl methacrylate. An isocyanato-urethane methacrylate has been synthesized from 2-hydroxyethyl methacrylate in connection with dental materials research in which the preparation of poly functional monomers for improvement of interfacial bonding with tooth tissue is a topic of some interest. 

An alternative method of producing natural rubber based clay reinforced nanocomposites with outstanding properties is by using a spray drying technique. In this technique the siUcate layers of clay will be well dispersed in an irradiated polymer latex and this mixture will be sprayed through hot air to produce micrometre-sized liquid droplets. When the solvent is fully evaporated, micrometre-sized polymer spheres with delaminated clay silicate layers on their surface are produced. These spheres can later be melt blended with natural rubber to produce ternary nanocomposites. It is noteworthy that exfoliation of nanofillers can still be achieved without modification of the nanofiller surface, thus the expensive modification process can be eliminated. 

The lENs (interpenetrating elastomer networks) are blends of two kinds of latexes, both of which are pre-cross-linked. The surface modification grafts involve grafting of polymer 2 onto the surface of a polymer 1, often to alter the surface characteristics of the material such as contact angle, polarity, or bondability. 

The nanoscale coating of colloid particles with materials of different compositions has been an active area of research in nanoscience and nanotechnology [2]. Deposition of metal nanoparticles on different colloid particles to form core-shell particles has been one of the most effective tools for achieving such composite nanostructures [172]. In particular, a number of studies on such composite structures were concentrated on the fabrication of metal coated latex particles, because of their potential applications in the fields of surface-enhanced I man scattering (SERS), catalysis, biochemistry, and so forth [173]. Conventionally, silver shells on polymer latex were prepared via wet-chemistry methods, which involve the activation of a latex surface by seeds of a different metal, followed by the deposition of the desired metal [174], or the modification of the latex with groups capable of interacting with the metal precursor ions on the latex surface via complex or ion pairs, and subsequent reduction [175]. 

Different approaches are used to prepare polymer particles with attaching to surface-functionalized groups. In majority of the cases, they consist of step-batch or -semibatch polymerizations in dispersed media, being among them pulsion polymerization (emulsifier-free or not) the most used polymerization process (i) emulsion homopolymerization of a monomer containing the desired functional group (functionalized monomer), (ii) emulsion copolymerization of styrene (usually) with the functionalized monomer, (iii) seeded copolymerization to produce composite functionalized latexes, and (iv) surface modification of preformed latexes. 

Kawaguchi et al. [118] proposed the modification by hydrolysis of the surface groups of mono-disperse acrylamide-styrene copolymer latex obtained by an emulsifier-free aqueous polymerization. In this way they obtained a series of polymer latexes having the same particle size but different kinds and amounts of functional groups on the particles surfaces. 

Min, K., Hu, J., Wang, C., and Flaissari, A. 2002. Surface modification of polystyrene latex particles via atom transfer radical polymerization. J. Polym. Sci. Part A Polym. Chem. 40 892-900. 

In the context of polymers in industrial applications a number of key issues can be identified that are amenable to direct investigation and analysis by AFM approaches. From the preceding chapters the potential of probe microscopic techniques to conveniently visualize for instance surface (or bulk) morphologies and filler distributions has become obvious. Different classes of polymer materials, such as for instance thermoplastics, latexes, porous materials for membranes or thin films are subjected to different types of processing and treatments. The impact of all these modifications and the dependence on the process parameters can hence be closely monitored and in many cases quantitatively characterized by AFM. 

---