Swelling–shrinking behavior of hydrated noncross‐linked copolymer films in response to photoreversible isomerizaton and metal complexation of spiropyran units of the copolymers

Abstract

The copolymer of hydroxypropyl methacrylate (HPMA) and photochromic spiropyran methacrylate (SPMA) has been synthesized. The films of the copolymer (P(HPMA-SPMA)) in a hydrated state showed reversible swelling-shrinking behavior in response to photoreversible isomerization and metal complexation of SPMA units in spite of covalently noncross-linked copolymers. In addition, the protonated open form of the SPMA units of the copolymer was possibly stabilized thermodynamically by the HPMA units from ultraviolet-visible absorption measurement of the hydrated P (HPMA-SPMA) film. On the other hand, the difference in color of the hydrated films between P(HPMA-AABMA) and P (NIPMA-AABMA), which was a copolymer of N-isopropyl methacryl amide (NIPMA) and azobenzene methacrylate (AABMA) as a pH indicator, was suggestive of the interference of the proximal hydroxyl groups of the immobilized HPMA units with protonation of the AABMA units. The HPMA units of the copolymers also contributed to improvement of thermodynamic stability of the metal complexes with the SPMA units.

Synthesis of spiropyran-containing random copolymer by atom transfer radical polymerization and its complexation with metal ions

“…Takayuki Suzuki synthesized random copolymer P(SPMA-co-HPMA) and explored its complexation with Cu 2+ in solution with pH 5. [34] This report described metal complexation of SPMA unit in spite of covalently non-cross-linked structure, and the comonomer HPMA segment could stabilize the protonated open form of SPMA unit thermodynamically.…”

Computational modelling and investigation of mechanical and electrochemical response of photo-sensitive hydrogels

“…It is demonstrated in the published findings that the metal ion adsorption of hydrogel might highly depend on the hydration of polymeric backbone materials [214]. Therefore, apart from PSBMA, another two reported spiropyran-modified copolymers are investigated in this section, in order to examine the effect of polymeric materials on the metal ion complexation response, including hydroxypropyl methacrylate (HPMA) [214] and N-isopropylacrylamide (NIPAAm) [115,215]. The hydration difference among the three polymeric materials is characterized by the interactive parameter and the coefficient .…”

“…The hydration difference among the three polymeric materials is characterized by the interactive parameter and the coefficient . HPMA is a hydrophobic polymer, where is given as 0.592 [216] and is estimated as 1.3×10 -4 mM -1 by fitting the swelling size change of a spiropyran-loaded HPMA film after visible irradiation [214]. Regarding Figure 4.8(c) and (f).…”