The swelling equilibria of four different N-(alkoxyalkyl) acrylamide gels in water were measured at various temperatures. The N-3-(methoxypropyl)acrylamide (NMPA) gel hardly changed its volume upon heating. Three gels (N-(2-ethoxyethyl)acrylamide (NEEA), N-(3-ethoxypropyl)acrylamide (NEPA), and N-(tetrahydrofurfuryl)acrylamide (NTFA) gels) exhibited reentrant type swelling curves of a swollen-shrunkenswollen cycle in water in response to a change in temperature. The gradual shrinking of the NEEA,NEPA,and NTFA gels upon heating within the temperature range 25-35 °C was considered to be due to the weak hydrophobic interaction based on the alkoxyalkyl groups, while the subsequent swelling at higher temperatures was due to the thermal mixing which dominated the hydrophobic interaction. These discussions were supported by preliminary calculations introducing the temperature dependence of hydrophobic interaction into the ΔF term of Tanaka's equation.
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