The effects of gas-phase oxygen on the weight loss of poly (methyl methacrylate) (PMMA) were studied by comparing weight loss behavior of PMMA degraded in nitrogen with that of PMMA degraded in air. Thermogravimetry (TG) and isothermal heating experiments were conducted to obtain kinetic constants for the degradation of PMMA. The results show that there are two distinct effects of oxygen on the weight loss of PMMA; one is an increase in PMMA stability at low temperatures and the other is a destabilization of PMMA at high temperatures by enhanced random scission. There are two reaction stages for the weight loss from PMMA degraded in nitrogen and four reaction stages for PMMA degraded in air. These four reaction stages are, however, caused mainly by impurities in the sample. The effects of purification of the commercial PMMA on the weight loss are small for samples degraded in nitrogen, but they are significant for samples degraded in air.

The mechanisms of thermal degradation and thermal oxidation of poly(methyl methacrylate) (PMMA) were studied by measuring the molecular weight of rapidly quenched samples thermally degraded in nitrogen and air in the range of temperatures between 200 and 325 °C. Results show that thermal oxidation reduces the degree of polymerization much faster than does thermal degradation. Random scission is the initiation step for both thermal degradation and oxidative degradation. The activation energy for the random scission initiation is 233 kJ/mol for thermal degradation and 64 kJ/mol for oxidative degradation. The average zip length decreases from 2620 to 1340 with an increase in temperature from 258 to 324 °C for thermal degradation. However, the average zip length increases from 20 to 102 with an increase in temperature from 205 to 251 °C for thermal oxidative degradation. A reasonable value of activation energy for the termination reaction in nitrogen, 104 kJ/mol, is obtained only for the assumption of first-order termination.

Although many kinds of synthetic polymers have been investigated to construct blood-compatible materials, only a few have achieved success. To establish molecular designs for blood-compatible polymers, the chain structure and dynamics at the water interface must be understood using solid evidence as the first bench mark. Here we show that polymer dynamics at the water interface impacts on structure of the interfacial water, resulting in a change in protein adsorption and of platelet adhesion. As a particular material, a blend composed of poly(2-methoxyethyl acrylate) (PMEA) and poly(methyl methacrylate) was used. PMEA was segregated to the water interface. While the local conformation of PMEA at the water interface was insensitive to its molecular weight, the local dynamics became faster with decreasing molecular weight, resulting in a disturbance of the network structure of waters at the interface. This leads to the extreme suppression of protein adsorption and platelet adhesion.

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Poly(2-methoxyethyl acrylate) (PMEA) exhibits excellent blood compatibility. To understand why such a surface functionality exists, the surface of PMEA should be characterized in detail, structurally and dynamically, under not only ambient conditions, but also in water. However, a thin film of PMEA supported on a solid substrate can be easily broken, namely it is dewetted. Our strategy to overcome this difficulty is to mix PMEA with poly(methyl methacrylate) (PMMA). Differential scanning calorimetry and cloud point measurements revealed that the PMEA/PMMA blend has a phase diagram with a lower critical solution temperature. The blend surface was also characterized by X-ray photoelectron spectroscopy in conjunction with microscopic observations. Although PMEA is preferentially segregated over PMMA at the blend surface due to its lower surface free energy, the extent of segregation in the as-prepared films was not sufficient to cover the surface. Annealing the blend film at an appropriate temperature, higher than the glass transition temperature and lower than the phase-separation temperature of the blend, enabled us to prepare a stable and flat surface that was perfectly covered with PMEA.