Hi everyone,
I prepared some new copolymers of Poly(N,N-Dimethylamino-2-Ethyl Methacrylate) (PDMAEMA) via its graft copolymerization to hydrophobically modified polymers via ATRP. When I took the LCST of these polymers, suprisingly I found that in the same pH, the LCST of these polymers (around 80-95oC) was much higher that that of homo-PDMAEMA (45-50oC). Can anyone justify this observation?
In fact, at first I prepared Cellulose-Palmitate (with DS=1.2 of palmitate groups) to have a hydrophobically modified cellulose. Then I inserted ATRP initator (DS = 0.11), onto the Cellulose-Palmitate backbone. Finally, I polymerized various amounts of DMAEMA from this macroinitiator via ATRP. I mean, various length of PDMAEMA was grafted onto the cellulose-palmitate. When the grafted PDMAEMA was too small the resulted graft copolymer was not soluble in water. But when the PDMAEMA grafted chains have sufficient molecular weight to dissolve the graft copolymer in water (at pH=7), the LCST of the graft copolymer was much higher than that of PDMAEMA. I can not justify this observation!!
Dear all;
two factors may contribute to this delay of LCST and that should be considered. These are the grafts density and length. In general high grafts density and lengths will contribute more to the packing of the matrix. Regards
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