研究目的
To investigate the effect of alumina and modified alumina nanoparticles on the glass transition temperature (Tg) of PMMA/alumina nanocomposites using molecular dynamics simulations.
研究成果
The addition of alumina to the PMMA decreases its Tg but adding the modified alumina to the PMMA increases its Tg. The mobility of polymer chains and the thermodynamic properties show that adding the alumina to the PMMA can increase the mobility of polymer chains, decrease the free volume and reduce the energy system and the interaction between polymer chains. Adding functionalized alumina to the polymer reduces the mobility of polymer chains and leads to an increase in the Tg.
研究不足
The inconsistency observed between the experimental and the simulation results can be attributed to the difference in the simulation cooling rates and experimental method. Further study would be useful by incorporating other key variables including the interphase of nanocomposite and other functionalize group into simulations.
1：Experimental Design and Method Selection:
Molecular dynamics simulations were performed using the Materials Studio 6.0 software package of Accelrys. The compass force field was applied for all atoms. The Berendsen thermostat and the Anderson thermostat were utilized to control pressure and temperature, respectively. Periodic boundary conditions were applied to reduce surface effects.
2：0 software package of Accelrys. The compass force field was applied for all atoms. The Berendsen thermostat and the Anderson thermostat were utilized to control pressure and temperature, respectively. Periodic boundary conditions were applied to reduce surface effects.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: Three polymer-based systems including PMMA, PMMA/alumina (PA), and PMMA/functionalized alumina (PFA) nanocomposites were studied. The polymer chain was considered with a degree of polymerization of 50 based on all atom model and the α-alumina nanoparticle was assumed spherical with a radius of 5 ?.
3：List of Experimental Equipment and Materials:
Materials Studio 6.0 software package of Accelrys was used for simulations.
4：0 software package of Accelrys was used for simulations.
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: The system was equilibrated for 300 ps at a temperature of 1000 K in NPT ensemble. Annealing was conducted using the NVT ensemble for ten cycles. The system was cooled from 500 K to 300 K to determine the Tg.
5：Data Analysis Methods:
The variation of density versus temperature was obtained to determine the Tg. The mobility of the chain segments was investigated based on the mean square displacement and radius gyration.
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