Modified bulk polymerization

LVDT linear velocity displacement transducer MBP modified bulk polymerization... 

A semi-interpenetrated network was obtained by bulk polymerization of 2-hydroxye-thyl methacrylate incorporated in DMF treated PET films by solvent-exchange technique, followed by treatment of films in e-lectrical discharges. Heparinization was accomplished by reacting glutaraldehyde with heparin and poly(2-hydroxyethyl methacrylate) present on the surface of modified polyester films. The immobilization of heparin was indirectly evidenced by chromatographying the silylated hydrolyza-tes of heparinized PET films and heparin, respectively. In vitro experiments demonstrated the enhanced thromboresistance of heparinized films. 

At AWE, the Lewis acid-catalyzed bulk polymerization route has been the main synthesis route to poly(m-carborane-siloxane) elastomers. Our selection has been based on considerations of safety, availability of key reagents, and ease of scale-up operations. An understanding of the physical and chemical properties of these materials, and how these properties can be modified through the synthesis process, is essential in order to develop materials of controlled characteristics. 

The thermal stability of poly(vinyl chloride) is improved greatly by the in situ polymerization of butadiene or by reaction with preformed cis-1,4-polybutadiene using a diethyl-aluminum chloride-cobalt compound catalyst system. The improved thermal stability at 3-10% add-on is manifested by greatly reduced discoloration when the modified poly-(vinyl chloride) is compression molded at 200°C in air in the absence of a stabilizer, hydrogen chloride evolution at 180°C is retarded, and the temperature for the onset of HCl evolution and the peak decomposition temperature (DTA) increase, i.e. 260°-280°C and 290°-325° C, respectively, compared with 240°-260°C and 260°-280°C for the unmodified homopolymer, in the absence of stabilizer. The grafting reaction may be carried out on suspension, emulsion, or bulk polymerized poly(vinyl chloride) with little or no change in the glass transition temperature. 

FIGURE 11.20 TGA curves and the CCA curves for pure polystyrene and three PS/clay nanocomposites obtained with in situ bulk polymerization, VB16 and OH16 are two ammonium-modified MMT and P16 is phosphonium-modified MMT. (From Zhu, J. et al., Chem. Mater., 13, 3774, 2001. With permission.)... 

However, the introduction of the solvent into the polymerization medium poses new problems. The solvents must be pure, without inhibiting and transfer agents. Every solvent takes part in the polymerization process its effect is almost never limited to the mere physical dilution of the monomer. It solvates the active centres it participates in processes connected with energy and impulse transfer often it serves as a transfer agent (so that the degrees of polymerization of solution-polymerized products are usually lower compared with bulk-polymerized polymers) it may form complexes with some component of the system it modifies initiation efficiency by the cage effect etc. 

Ferrocene modified flexible polymeric electron transfer systems Ferrocene and its derivatives are readily available and commonly used organometalUc redox mediators, so it is quite natural that they were selected first to synthesize mediator modified polymeric electron transfer systems. Siloxane pol5uners are flexible but aqueous insoluble pol3nmers. As previously indicated, a flexible polymer backbone allows close contact between the redox center(s) of the enzyme and the mediator, and the water insoluble property of the polymer prevents not only redox polymer from leaching into bulk media but also prevents enzyme diffusion away fi-om the electrode surface by entrapping it in the polymer/carbon paste matrix. Therefore, ferrocene and... 

The photopolymerization of methyl methacrylate using a quinoline-chlorine charge-transfer complex has been investigated. Bulk polymerization was found to follow normal free-radical kinetics, whereas in solution variable monomer exponents were observed depending on the nature of the solvent. The kinetic nonideality in solution was attributed to retardation and initiator termination via degradative chain-transfer involving solvent-modified initiating complexes and chain radicals. 

In bulk polymerization the reaction mixture consists essentially of the monomer and, in the case of chain growth polymerization, a soluble initiator and possibly modifiers. In the case of homogeneous bulk... 

Bulk polymerization initiated via more novel methods have also been used to form bulk PS-MMT nanocomposites. Zhang et al. [19] used gamma irradiation to initiate the polymerization of PS-MMT nanocomposites with different surface modifications (3, 34) and successfully prepared exfohated morphologies when reactive clay modifications were used. Uthirakumar et al. [51-54] modified MMT with a cationic radical initiator which was used to initiate the bulk polymerization of styrene. Because the polymerization was initiated from the clay surface and the monomer and the clay were suitably compatible, exfoliated morphologies were formed. 

PMMA modified by inorganic nanoparticles such as Ti02, ZnS Mn, CdSe, CdSe/ZnS, ZnO, and CNTs has led to enhanced optical [16], thermal [149], and electrical properties, as compared to pure polymer. For example, Althues et al. [16] reported an efficient method for generation of completely transparent and strongly luminescent ZnS Mn/PMMA nanocomposites. They used in-situ bulk polymerization of transparent dispersions containing ZnS Mn nanoparticles in a mixture of MMA and AA the effective diameter of nanoparticles in the monomer dispersion was 22 nm. Two factors were responsible for the stability of the ZnS Mn/monomer dispersion, i.e., coordination of AA, which modified the surface of the nanoparticles and led to hydrophobization, and adsorption of ions leading to a surface charge... 

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