The present article considers the coil-to-globule transition behavior of atactic and syndiotactic poly(methyl methacrylates), (PMMA) in their theta solvent, n-butyl chloride (nBuCl). Changes in Rh in these polymers with temperature in dilute theta solutions were investigated by dynamic light scattering. The hydrodynamic size of atactic PMMA (a-PMMA-1) in nBuCl (Mw: 2.55 × 106 g/mol) decreases to 61% of that in the unperturbed state at 13.0°C. Atactic PMMA (a-PMMA-2) with higher molecular weight (Mw: 3.3 × 106 g/mol) shows higher contraction in the same theta solvent (αη = Rh(T)/Rh (θ) = 0.44) at a lower temperature, 7.25°C. Although syndiotactic PMMA (s-PMMA) has lower molecular weight than that of atactic samples (Mw: 1.2 × 106), a comparable chain collapse was observed (αη = 0.63) at 9.0°C.
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G�rel et al. (1999) studied this question.
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