Fluorescence study on the phase transition of hydrogen-bonding gels

A technique based on steady-state fluorescence measurements is introduced to study the discontinuous volume phase transition of hydrogen-bonding gel. The fluorescence light intensity of pyranine (1-Hydroxypyrene-3, 6, 8-trisulfonic acid) bonded to the gel by means of methacryl amino-propyl-trimethyl ammonium chloride was monitored during the swelling of poly(methacrylic acid-co-dimethyl acrylamide) copolymer in water as a function of temperature. A discontinuous volume phase transition around 60 °C and an additional phase around 30 °C, which may be interpreted as the freely fluctuating phase in a collapsed state, were observed when the fluorescence intensity changes.