A derivative of 1,1‘-binaphthyl (BN) was appended to poly(methacrylic acid) (PMA), and
its reversible complexation with γ-cyclodextrin (CyD), which leads to an induced circular dichroism signal
(ICD), was studied as a function of pH. The ICD was observed at pH above 6 but disappeared sharply at
lower pH's where clustering of the chain led to encapsulation of the BN by the polyelectrolyte and
prevented the approach of the CyD. Kinetic work based on the atropisomeric character of the BN showed
the capsule to exert a strong and pH dependent restriction on the racemization of the BN. In syndiotactic
PMA the racemization followed first-order kinetics at all pH values while, with atactic PMA as the carrier,
the racemization at low pH was biphasic. Remarkably, the most restrictive relationship between the
polyelectrolyte and the racemization of the probe is found at a degree of ionization just slightly below the
point where the chain charge density disrupts the capsules. The behavior of the BN label appended to
PMA was compared with its behavior when attached to poly(acrylic acid), poly(2-ethylacrylic acid), and
an alternating maleic acid−butyl vinyl ether copolymer.
Association between copolymers of p‐styrenesulfonate (Cs+)/3‐methacryloxypropyltrimethoxysilane [copolySS(Cs+)/MAPTMS], and hydroxypropylcellulose (HPC) are shown to exist in dilute aqueous solution. Gels form at concentrations as low as 0.05 g/dL. The tendency to form gels is a function of mol % MAPTMS in the copolymer and molecular weight of HPC. Gels can be dispersed by the addition of dimethylformamide (DMF), a known disruptor of hydrogen bonding. Homopolymers of SS(Cs+) and MAPTMS were also prepared. PolyMAPTMS shows anamolous behavior with regards to association with HPC in that gels form to a lesser degree than the trend exhibited by the copolymers. This is rationalized on the basis of the lack of chain expansion due to the absence of salt groups and their intrapolymer repulsions. In addition to the hydrodynamic data, the phase relationship of blends of HPC with either copolySS(Cs+)/MAPTMS, polySS(Cs+), or polyMAPTMS cast from aqueous solution strongly suggests specific interactions between polymers.
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