Phase Behavior of Aqueous
Solutions of Copolymers
of <i>N</i>,<i>N</i>′-Diisopropylfumaramide
and <i>N</i>-Isopropylacrylamide: Effect of the Density
of Side Chains
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Abstract
This letter describes the phase behavior of aqueous solutions
of
an <i>N</i>-isopropylacrylamide (NIPAM) homopolymer and
copolymers of <i>N</i>,<i>N</i>′-diisopropylfumaramide
(DIPFAM) and NIPAM as studied by transmittance measurements, infrared
spectroscopy, and differential scanning calorimetry to reveal the
effect of the density of <i>N</i>-isopropylamide side chain
upon the phase behavior. The clouding-point and clearing-point temperatures
decreased with increasing the mole fraction of DIPFAM (<i>x</i><sub>D</sub>). It was noteworthy that only an extra side chain per
ca. 7 NIPAM units had a remarkable effect on the phase behavior; the
interactions between side chains were stronger, the intrapolymer contraction
was less favorable, and the cooperativity of phase transition was
lower at <i>x</i><sub>D</sub> = 0.15 presumably because
of the steric hindrance of dense side chains
