The use of hydrophobic spacers in the development of new temperature‐ and pH‐sensitive polymers

Abstract The preparation and characterization of two series of methacrylic acid derivative polymers is described. One series contains aliphatic spacers with one to ten methylene units, while the other series includes an aromatic ring with changes in the position of the acid, as spacer. Both series of polymers were obtained as methoxy‐ester protected acid polymers and as polymers containing free acid groups in different amounts. pH‐sensitive gels and temperature‐sensitive N ‐isopropylacrylamide (NIPAAm) copolymers were prepared by using some of the monomeric structures described. The pH of the swelling transition of the gels changed from 3.5 up to 9.0 as a function of the spacer length and type. The lower critical solution temperature (LCST) of NIPAAm copolymers in water was lowered from 33.6°C to 6°C as a function of the co‐monomer content and type. The observed changes in the pH of the swelling transition of gels and in the LCST of NIPAAm copolymers can only be explained if hydrophobic‐hydrophobic and hydrogen‐bonding interactions are considered in connection with the specific chemical structure of the monomers used.