A carbon-13 nuclear magnetic resonance study of the triad sequence structure of block and statistical copolymers of ethylene oxide and propylene oxide

Thermodynamics of micellization of tapered statistical copolymers of ethylene oxide and propylene oxide in water

“…Absolute M n values of the copolymers were obtained by 13 C NMR spectroscopy by comparison of the integrals of resonances from the carbons of end groups and backbone groups, based on the assignments of Heatley et al [10]. Denoting the two copolymers prepared as t-E/P38 and t-E/P30 (t meaning tapered statistical and the number being the overall mol% P), values of M n were 5180 and 4920 g mol −1 , respectively, and their P contents were 0.45 and 36 wt%, respectively.…”

Anionic polymerisation of propylene oxide. Investigation of double‐bond and head‐to‐head content by NMR spectroscopy

“…OHf + 0-K; t OHO-K+ (24) with equilibrium constant: (25) where the subscript f denotes non-H-bonded species. If the hydrogen bonded ion pairs contribute to propagation (which depends on nucleophilicity) but not to transfer (which depends on base strength) then the conditions under which C,, (hence r) tends to a low value correspond to low concentrations of free ion pairs [0 -K;], i. e. to high concentrations of hydroxyl groups and so high proportions of H-bonded ion pairs.…”

“…Several g r o~p s~' -~~) , most recently Heatley et al 24) have used 13C NMR to show that propagation by headto-tail (HT) addition is the norm, the proportion of HT placements being well above 90%. The predominant terminating group is secondary OH, i.e.…”

“…A small proportion of additions result in head-to-head (HH) and tail-to-tail (TT) placem e n t~,~~~~) , any HH addition being immediately followed by TT addition24). In the present work CH and CH, I3C NMR subspectra obtained by the distortionless enhancement by polarization transfer (DEFT) technique 23,24) were used to monitor the proportion of HH and TT placements.…”

Aluminium and rare earths alkoxides as initiators for the heterogeneous anionic coordinated polymerisation of propylene oxide. A1H NMR approach of the regioselectivity and transfer ability of the catalytic system

“…All resonances being assigned previously by Schilling and Tonelli 14) and Heatley 15) , we recently proposed a method that gives a quantitative determination of the regioselectivity induced by the catalyst system 3) . This determination is a prerequisite for a reliable approach to the tacticity distribution in regular sequences.…”