The effect of temperature perturbation on a single-chain-collapse process was studied for poly(methyl methacrylate) with the molecular weight M w=1.05×107 in the mixed solvent of tert-butyl alcohol+water (2.5 vol%). In the chain-collapse process after a quench from the θ temperature to a temperature T1, the temperature was changed from T1 to T2 at the time t1 after the quench and returned to T1 at the time t1+t2. In the three stages at T1, T2, and T1, measurements of the mean-square radius of gyration of polymer chains were carried out by static light scattering and the chain-collapse process was represented by the expansion factor as a function of time. An effect of chain aggregation on the measurements was negligibly small because of the very slow phase separation. For the negative temperature perturbation (T1>T2), the chain-collapse processes observed in the first and third stages were connected smoothly and agreed with the collapse process due to a single-stage quench to T1. A memory of the chain collapse in the first stage at T 1 was found to persist into the third stage at the same temperature T1 without being affected by the temperature perturbation of T 2 during t2. The memory effect was observed irrespective of the time period of t2. The positive temperature perturbation (T1<T2) showed an acceleration of the chain-collapse process.
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