Photoresponsive polymers

A composition that expands or contracts upon a change in exposure to light energy, which comprises:

• a polymeric material having an inverse temperature transition, wherein at least a fraction of the bioelastomeric repeating units in said polymer contain a photoresponsive side chain that responds to a change in exposure to light energy to effect a change in the polarity or hydrophobicity of the side chain and that is present in sufficient amount to provide a shift in the temperature of inverse temperature transition of the polymer upon the change in exposure to light energy.

A method of producing mechanical work, which comprises:

• changing light energy exposure on a bioelastic polymer containing bioelastomeric units having an inverse temperature transition, wherein at least one amino acid residue in a bioelastomeric unit has a side chain that responds to a change in exposure to light energy to effect a change in the polarity or hydrophobicity of the photoresponsive side chain and that is present in sufficient amount to provide a shift in the temperature of inverse temperature transition of the polymer upon the change in exposure to light energy, and wherein said polymer is constrained so that expansion or contraction of said polymer produces mechanical work.

A method of producing a pH change in an environment, which comprises:

• locating in said environment a bioelastic polymer containing bioelastomeric units having an inverse temperature transition, wherein (1) at least one amino acid residue in a bioelastomeric unit has a side chain that reacts to a change in exposure to light energy to effect a change in the polarity or hydrophobicity of the photoresponsive side chain and that is present in sufficient amount to provide a shift in the temperature of inverse temperature transition of the polymer upon the change in exposure to light energy, and (2) at least a fraction of said bioelastomeric units contain at least one amino acid residue with a side chain capable of undergoing reversible protonation, and
• applying a change in exposure to light energy to said environment, whereby the light energy change causes a change in the pKa of the polymer and a resulting change of pH in the environment.

An apparatus for producing changes in pH in an environment, which comprises:

• a bioelastic polymer containing bioelastomeric units having an inverse temperature transition, wherein (1) at least one amino acid residue in a bioelastomeric unit has a side chain that reacts to a change in exposure to light energy to effect a change in the polarity or hydrophobicity of the side chain and that is present in sufficient amount to provide a shift in the temperature of inverse temperature transition of the polymer upon the change in exposure to light energy;
• and
• means for applying a change in exposure to light energy to said polymer, whereby the change in light energy causes said polymer to undergo a change in pKa and change the pH in the environment.