Poly PMMA composites

Polythiophene lends itself to the same routes to composites. A poly(3-methyl-thiophene)-poly(methylmethacrylate) composite has been made by electrochemical polymerization from a solution of thiophene and PMMA in methylene chloride and nitrobenzene. At high current densities the electrode side quickly became highly conducting while the outer side was less so 307). Similar composites have been prepared by chemical routes, using a Grignard reaction, firstly to couple the thiophene units in a step-reaction, then to initiate the polymerization of the methyl methacrylate 315). 

Jin et al. (65) used poly(vinylidene fluoride) (PVDF) as a compatibilizer to assist dispersion of CNTs in PMMA. Multi-walled carbon nanotubes were first coated with PVDF and then melt-blended with PMMA. Poly(vinylidene fluoride) served as an adhesive to improve wetting of CNTs by PMMA and to increase the interfacial adhesion resulting in improved mechanical properties of MWCNT-PMMA composites. 

Kim et al. (66) used poly(3-hexylthiophene) (P3HT)-graft-PMMA as a compatibilizer to prepare MWCNT-PMMA composites by solution blending. The CNT content was varied from 0.01 to 0.1 wt%. The resulting composites showed improved tensile strength and modulus. 

The resulting PMMA composite materials are insoluble in both organic or aqueous media. Hence alternative acrylates soluble even in their polymerized state have been sought for. Especially poly-tert-butyl acrylates suit weU to this purpose. Furthermore, the tert-butyl residues are easy to remove from these composites, so water soluble polyacrylic acids with additional carbon nanotubes are obtained. 

Figure 4.23 (a) Typical electrical responses of PANI/PMMA composite nanofibers to TEA vapors of different concentrations (doping acid TSA). (b) Sensing magnitude of PANI/PMMA composite nanofibers with different diameters as a function of the concentration of TEA vapor. Concentration ofelectrospun PMMA solution (a) 0.32 g ml and (b) 0.18 g ml (Reprinted with permission from Sensors and Actuators B., Gas sensing properties of a composite composed ofelectrospun poly(methyl methacrylate) nanofibers and in situ polymerized polyaniline byS.Ji, Y. Li and M. Yang, 133, 644-649. Copyright (2008) Elsevier Ltd)... 

Figure 6.15 Atomic force microscopy images of gold patterns prepared from micro- and nanopattemed poly(styrene-b-2-vinyl pyridine) (PS-b-P2VP) (a), PS-b-P2VP/poly(methyl methacrylate) (PMMA) thin films with PMMA composition of 10wt% (b), 20 wt% (c),...

Various approaches have been developed to improve the solubility of NTs in different polymer matrices. The addition of 1 wt% non-ionic surfactants improves, for instance, the glass transition temperature. Moreover, the elastic modulus increased by more than 30% relative to the absence of a surfactant [76]. In the presence of 0.5 wt% poly(vinylene fluoride) (PVDF) the storage modulus of MWNTs/PMMA composites was significantly improved at low temperatures [77]. 

Micro- and nano-scale silica particles filled poly (methyl methacrylate) (PMMA) composites were prepared using high shear compounding and thin-wall micromolding. Mechanical performances of the composites were elucidated through tensile tests and internal structures of fractured surfaces were obtained from microscopic observations. The incorporation of silica particle has raised the tensile modulus of all specimens irrespective of processing conditions. Distribution of micro-fillers in the molded specimens was preferential towards the end side than the gate and center sides. Nano-filler particles were dispersed uniformly in most parts of the specimen while boundary separations between filler and matrix could be observed at the skin layer in micro sihca filled PMMA. This led to an assumption that there was better filler-matrix adhesion in nano-filler composites than in micro-filler composites. 

Unlike most crystalline polymers, PVDF exhibits thermodynamic compatibiUty with other polymers (133). Blends of PVDF and poly(methyl methacrylate) (PMMA) are compatible over a wide range of blend composition (134,135). SoHd-state nmr studies showed that isotactic PMMA is more miscible with PVDF than atactic and syndiotactic PMMA (136). MiscibiUty of PVDF and poly(alkyl acrylates) depends on a specific interaction between PVDF and oxygen within the acrylate and the effect of this interaction is diminished as the hydrocarbon content of the ester is increased (137). Strong dipolar interactions are important to achieve miscibility with poly(vinyhdene fluoride) (138). PVDF blends are the object of many papers and patents specific blends of PVDF and acryflc copolymers have seen large commercial use. 

The soapless seeded emulsion copolymerization method was used for producing uniform microspheres prepared by the copolymerization of styrene with polar, functional monomers [115-117]. In this series, polysty-rene-polymethacrylic acid (PS/PMAAc), poly sty rene-polymethylmethacrylate-polymethacrylic acid (PS/ PMMA/PMAAc), polystyrene-polyhydroxyethylmeth-acrylate (PS/PHEMA), and polystyrene-polyacrylic acid (PS/PAAc) uniform copolymer microspheres were synthesized by applying a multistage soapless emulsion polymerization process. The composition and the average size of the uniform copolymer latices prepared by multistage soapless emulsion copolymerization are given in Table 11. 

In another study, uniform composite polymethyl-methacrylate/polystyrene (PMMA/PS) composite particles in the size range of 1-10 fim were prepared by the seeded emulsion polymerization of styrene [121]. The PMMA seed particles were initially prepared by the dispersion polymerization of MMA by using AIBN as the initiator. In this polymerization, poly(7V-vinyl pyrolli-done) and methyl tricaprylyl ammonium chloride were used as the stabilizer and the costabilizer, respectively, in the methanol medium. Seed particles were swollen with styrene monomer in a medium comprised of seed particles, styrene, water, poly(7V-vinyl pyrollidone), Polywet KX-3 and aeorosol MA emulsifiers, sodium bicarbonate, hydroquinone inhibitor, and azobis(2-methylbu-... 

It should be noted that by immobilizing the metal complex catalysts on carbochain polymers it is possible to prepare polymer-polymer compositions using PVC, PMMA, poly(vinyl acetate), etc., as the polymeric fillers [286-287]. 

With diblock copolymers, similar behavior is also observed. One component is enriched at the surface and depending on miscibility and composition a surface-induced ordered lamellar structure normal to the surface may be formed. Recent investigations include poly (urethanes) [111], poly(methoxy poly (ethyleneglycol) methacrylate)/PS [112] and PS/PMMA [113, 114]. In particular the last case has been extensively studied by various techniques including XPS, SIMS, NR and optical interferometry. PS is enriched at the surface depending on blockcopolymer composition and temperature. A well ordered lamellar structure normal to the surface is found under favourable conditions. Another example is shown in Fig. 6 where the enrichment of poly(paramethylstyrene), PMS(H), in a thin film of a di-... 

Various substituted styrene-alkyl methacrylate block copolymers and all-acrylic block copolymers have been synthesized in a controlled fashion demonstrating predictable molecular weight and narrow molecular weight distributions. Table I depicts various poly (t-butylstyrene)-b-poly(t-butyl methacrylate) (PTBS-PTBMA) and poly(methyl methacrylate)-b-poly(t-butyl methacrylate) (PMMA-PTBMA) samples. In addition, all-acrylic block copolymers based on poly(2-ethylhexyl methacrylate)-b-poly(t-butyl methacrylate) have been recently synthesized and offer many unique possibilities due to the low glass transition temperature of PEHMA. In most cases, a range of 5-25 wt.% of alkyl methacrylate was incorporated into the block copolymer. This composition not only facilitated solubility during subsequent hydrolysis but also limited the maximum level of derived ionic functionality. 

Some work has been done on blends of ABC and AB or AC or AB C block copolymers, such as polystyrene-b-polybutadiene-b-poly(methyl methacrylate) (PS-h-PB-fc-PMMA) triblock terpolymers with PS-h-PB or PB-h-PMMA or other systems. Besides known morphologies for these block copolymers (though at other overall compositions with respect to the different chemical... 

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