Polymeric surfactants polymethyl methacrylate

Tphe surface activity of block copolymers containing dimethylsiloxane units as one component has received considerable attention. Silicone-poly ether block copolymers (1,2,3) have found commercial application, especially as surfactants in polyurethane foam manufacture. Silicone-polycarbonate (4, 5), -polystyrene (6, 7), -polyamide (8), -polymethyl methacrylate (9), and -polyphenylene ether (10) block copolymers all have surface-modifying effects, especially as additives in other polymeric systems. The behavior of several dimethylsiloxane-bisphenol A carbonate block copolymers spread at the air—water interface was described in a previous report from this laboratory (11). Noll et al. (12) have described the characteristics of spread films of some polyether—siloxane block co-... 

Studies involving the use of organically modified clay particles in heterophase polymerization are rather scarce. Indeed, we are aware of only two reports that combine the emulsion or suspension polymerization approaches and ion-ex-change reaction. In one of these reports, AI BA is immobiHzed in the clay interlayer region to yield exfoliation of MMT in the PMMA matrix through suspension polymerization [135]. In another relevant study, it was demonstrated that exfoliated structures could be obtained by post-addition of an aqueous dispersion of layered silicates (either MMT or laponite) into a polymethyl methacrylate latex suspension produced in the presence of suitable cationic compounds (cationic initiator, monomer or surfactant) [136]. Since the latex particles were cationic and the clay platelets anionic, strong electrostatic forces were developed at the polymer/clay interface. 

An alternative (and perhaps more efficient) polymeric surfactant is the amphipathic graft copolymer consisting of a polymeric backbone B (polystyrene or polymethylmethacrylate) and several A chains ( teeth ) such as polyethylene oxide. The graft copolymer is referred to as a comb stabilizer—the polymer forms a brush at the solid/liquid interface. The copolymer is usually prepared by grafting a macromonomer such as me-thoxy polyethylene oxide methacrylate with polymethyl methacrylate. In most cases, some polymethacrylic acid is incorporated with the polymethylmethacrylate backbone this leads to reduction of the glass transition of the backbone, which makes the chain more flexible for adsorption at the S/L interface. Typical commercially available graft copolymers are Atlox 4913 and Hypermer CG-6 (ICI). 

Sustainable and controlled syntheses of polymers and polyelectrolyte membranes have been carried out in IL/O microemulsions, where the corresponding monomeric organic compounds constitute the oil phase. For example, Yan and coworkers used MMA/[Cj2mim][Cl]/[bmim][BFJ microemulsion to carry out atom transfer radical polymerization (ATRP) reaction to generate polymethyl methacrylate (PMMA) [133]. When this reaction was carried out in conventional microemulsions, large quantity of surfactants was needed to stabilize these systems, which rendered the... 

It is clear from Eq. (18) that when the Flory-Huggins interaction parameter, X, is less than 0.5, i.e., the chains are in good solvent conditions, Gmix is positive and the interaction is repulsive, and it increases very rapidly with decreasing h, when the latter is lower than 2. This explains why polymeric surfactants such as Hypermer CG6 (a graft copolymer of polymethyl methacrylate backbone and PEO side chains, produced by ICI) is ideal for... 

Another graft copolymer that could be used for stabilization of suspensions is that based on polyfructose backbone on which several alkyl groups have been grafted (Inutec LiC 0.1), mentioned above for stabilization of emulsions. This polymeric surfactant was used to investigate the stability of polystyrene (PS) and polymethyl methacrylate (PMMA) suspensions in the presence of electrolytes [NaCl, CaCl2, and Al2(S04)3] [37]. Polystyrene latex... 

Sahoo and Mohapatra [66] studied the catalytic effect of the in situ developed Cu(II)-EDTA complex with ammonium persulfate on the surfactant-free emulsionpolymerization of methyl methacrylate. The rate ofpolymerization at 50 °C is proportional to the concentrations of Cu(II), EDTA, ammonium persulfate, and methyl methacrylate to the 0.35, 0.69, 0.57, and 0.75 powers, respectively. In addition, the apparent activation energy and activation energies of the initiator decomposition, propagation, and termination reactions, respectively, are 34.5,26.9,29, and 16 kJ mol. It was proposed that the complex just acts as an effective surfactant in stabilizing the polymethyl methacrylate nanoparticles nucleated during polymerization. Independent experiments are required to verify this speculation and clarify the related stabilization mechanism. 

Example 7.5 In an effort to graft gelatin with polymethyl methacrylate (PMMA), 2g of potassium persulfate and 20 g of gelatin are dissolved in water. This is added to 40 g of methyl methacrylate (MMA), and the reaction mass is made up to 500 cm. This recipe does not contain any surfactant and the polymerization at 70°C is found to give stable emulsion polymenzation. Experimental analyses of samples show a copious formation of gelatin grafts, which suppress the homopolymerization of MMA [29]. Explain this phenomenon through a kinetic model. 

---