Methacrylate

Abstract: The effectiveness of 4-methacryloxyethyl trimellitate anhydride (4-META) on the adhesion of an acrylic rod with etched dentine and enamel was studied. Etching of tooth substrates with a 10% citric acid-3% ferric chloride solution prior to the adhesion proved effective. Monomers with both hydrophobic and hydrophilic groups like 4-META promoted the infiltration of monomers into the hard tissue. The infiltrated monomers polymerized in situ and good adhesion with the tooth substrates took place. The tensile adhesive strength was 18 MPa on the etched dentine. Scanning electron microscopic studies suggested that the monomers possess affinity with the hard tissue. The good adhesion was not provided by the interlocking at the tubules as had been considered previously.

Abstract: Thermal analysis of solution cast mixtures of poly(viny1idene fluoride) (PVF2) and poly(methy1 methacrylate) (PMMA) has been carried out with various programmed temperature profiles. Results from experi- ments conducted in a quasi-equilibrium state show that PVF:! crystallizes in the mixture upon cooling. Further- more, depressions were observed in the melting and the crystallization temperatures. The melting point depression phenomenon is found to be explicable in terms of thermodynamic mixing of a crystalline polymer with an amor- phous polymer. To this end, an analytical expression appropriate to the crystalline-amorphous polymer pair is de- rived from Scott's equation for thermodynamic mixing of two polymers. From this expression the interaction pa- rameter for the polymer pair is found to be -0.295 at 16OoC, indicating that the system is compatible in the molten state. The depression of crystallization temperature which depends strongly on both the composition and the cool- ing rate is attributed to the ability of the PVF2 segments to migrate and to the change of composition in the melt during crystallization. For mixtures with a PVF2 content by weight of less than 0.5, it is possible to suppress the crystal transformation at room temperature with a moderate cooling rate. Finally, it is pointed out that because of the strong kinetic effects of cooling on the thermodynamic state of the mixture, caution should be exercised in the calorimetric study of compatibility of the polymer pair.

Abstract: The present Communication compares the thermosensitivity in dilute aqueous solutions of well-defined copolymers composed of 95% of 2-(2-methoxyethoxy)ethyl methacrylate (MEO2MA) and 5% of oligo(ethylene glycol) methacrylate (OEGMA, Mn = 475 g·mol-1) and poly(N-isopropylacrylamide) (PNIPAM) samples having similar degrees of polymerization and chain-ends. The thermoresponsive behavior of P(MEO2MA-co-OEGMA) was found to be overall comparable, and in some cases, superior to PNIPAM. Hence, P(MEO2MA-co-OEGMA) copolymers can be considered as ideal structures, which combine both the properties of poly(ethylene glycol) and PNIPAM in a single macromolecule.

Abstract: A methacrylate monomer having the phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC) was prepared by an improved method with good yield. MPC was copolymerized with n-butyl methacrylate (BMA). The polymer membranes were prepared from the poly(MPC-co-BMA) by a solution casting method. The membrane adsorbed water well and became a hydrogel structure even MPC mole fraction in the copolymer was 0.04. The water content of the hydrogel membrane increased with increase of MPC units and rise of temperature. These properties of the hydrogel membrane were attributed to the highly hydrophilic phospholipid polar group in the copolymer. Water soluble organic compounds and proteins whose molecular weights were below 104 permeated through the hydrogel membrane. However, the protein could not permeate when the molecular weight was higher than 105.