Studies of competition between end-to-end and end-to-interior reaction for an associating chain by Monte Carlo simulations

• Main Authors: Ming-Tsui Cheng, 鄭子銘
• Other Authors: Yu-Jane Sheng
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/79147678300930268589

碩士 === 國立臺灣大學 === 化學工程學研究所 === 92 === The kinetic of conformational fluctuations of an associating chain with three attractive sites at polymer is studied by Monte Carlo simulation. In our study, polymer can fluctuate between open state, closed state and mismatch state. We investigate the kinetics of conformational fluctuations for an associating polymer of chain length N with an attractive site at both ends (?and β) and another attractive site in the midpoint (γ) by Monte Carlo simulations. The binding energy of ?with β and γ are –ε1 and –ε2, respectively. We change the binding energy (ε1 and ε2). In case1, ε1 is 10 and ε2 is 15. In case2, ε1 is 15 and ε2 is 15. We obtain their rate constants and the melting curves. In case1, the polymer chains like to fluctuate mismatch state at low temperature and like to fluctuate open state at high temperature. When open state transfers to closed state or mismatch state, polymer needs to overcome binding energy. When closed state or mismatch state transfers to open state, polymer needs to overcome entropy loss. The rate constant from the open state to the closed state is independent of the temperature but proportional to N-2. The rate constant from the open state to the mismatch state is independent of the temperature but proportional to N-2.16. The rate constant from the closed state to the mismatch state is independent of the temperature but proportional to N-2.16 .On the contrary, km,o and kc,o are independent of chain length but proportional to and . The rate constant from the mismatch state to the closed state is proportional to . In case2, ε1 is equal to ε2. At low temperature, polymer is at closed state and mismatch state. When attractive site of polymer is end-to-end reaction, △S is proportional to N2. Similarly, when attractive site of polymer is end-to-interior reaction, △S is proportional to N2.16. Therefore, the probability of polymer at closed state will increase when the polymer chains increase. The probability of polymer at mismatch state will decrease when the polymer chains increase.