Thermoresponsive polymers undergo coil-to-globule transitions at lower critical solution temperatures (LCSTs), which are tuned by changing the ratio of hydrophilic to hydrophobic monomers or end groups. We studied the effects of amphiphilic end group placement on LCST on diblock copolymers (i.e. End1  -BlockA-BlockB-End2  , End1  -BlockB-BlockA-End2  ) prepared by living radical polymerization to allow block length and end group placement to be controlled. Coupling the hydrophilic end to the hydrophilic block increases the LCST while coupling the hydrophobic end on the hydrophobic block lowered the LCST. End group effects were also studied on a symmetrical tri-block copolymer (i.e. End2  -A-B-A-End2  ) and a three-arms star diblock copolymer (End2  -A-B)3  -Core  . The LCST of the symmetrical tri-block copolymers with hydrophilic chain ends was similar regardless of the block placement (End2  -A-B-A-End2  ~ End2  -B-A-B-End2  ) but with hydrophobic ends block placement affected the LCST by 15 �C. The star copolymer with 3 non-polar end groups showed a significant effect of block sequence.

Studies of a new approach to tune thermal stimulus release properties of copolymers

245th National Meeting (2013)

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