Structure control of thermosensitive porous gels with hydrophobic long side chains and their thermoresponsive properties

Stearyl acrylate (SA) porous gel with hydrophobic long side chains swells o r shrinks rapidly in orgainc solvents in response to temperature changes. S uch a swelling/shrinking of gel is caused by the order-disorder transition of SA side chains. The porous structure of SA gel which is prepared by util izing the phase separation can be controlled with the cross-linker concentr ation in preparing the gel. However, a low cross-linker concentration forms a non-porous gel which decreases the response rare. In order to solve thes e problems, the control of porous structure by copolymerizing methacrylic e ster with SA was examined experimentally. The thermoresponsive proper ties of these copolymer gels were also examined in 1-octanol. Four kinds of meth acrylic esters with different lengths of side chain, i.e., methyl-, ethyl-, hexyl- and dodecyl-metacrylate, were used. Even if the concentration of cr oss-linker was quite low, the porous gels were obtained by copolymerizing t hese methacrylic eaters at an adequate mole ratio;in the case that the mole ratio was less than 0.25, the porous structure was almost independent of t he length of side chain of the methacrylic ester. However, the crystalline structure of SA side chains in these gels largely depends on the length of the side chain of the methacrylic ester, and such a change of crystalline s tructure strongly affects the thermoresponsive properties.