Hydration Changes of Poly(2-(2-methoxyethoxy)ethyl Methacrylate) during Thermosensitive Phase Separation in Water

Abstract

Hydration changes of poly(2-(2-methoxyethoxy)ethyl methacrylate) (PMoEoEMa) during thermosensitive phase separation in water have been investigated by infrared spectroscopy. The C=O stretching band can be separated into three components assigned to non-hydrated carbonyl groups and singly and doubly hydrogen-bonded carbonyl groups (1728, 1709, and 1685 cm-1, respectively). Relatively large parts of the carbonyl groups (50% in 30 wt % solution) do not form hydrogen bonds even below the transition temperature (Tp) probably because they possess crowded positions near the backbone. The fraction of hydrogen-bonding carbonyl groups decreased during phase separation by approximately 0.2. Among five nu(C-H) bands, the highest- and the lowest-frequency bands (nu(C-H)A and nu(C-H)E) exhibited relatively large red shifts of 8 and 11 cm(-1), respectively. DFT calculations indicate that the formation of a H-bond between the ether oxygen and water leads to blue shifts of nu(C-H) of adjacent alkyl groups and has a larger effect than a direct H-bond to the alkyl groups, namely, C-H...O H-bonds. The fraction of hydrogen-bonding methoxy oxygens estimated from the position of the nu(C-H)A is 1 at <Tp and zero at >Tp. This result indicates that the methoxy oxygens and the carbonyl are more favorably hydrated than the other at <Tp and >Tp, respectively.

Study on hydration of poly(N-vinylcaprolactam) microgels by near-IR and mid-IR spectroscopy

“…The reason for the blue shift is essentially the same with that for the fundamental ν(C-H) frequencies. Both direct interaction between the alkyl groups [14] and water and hydrogen bonding of water to the carbonyl oxygen cause blue shift of the ν(C-H) bands and their overtones [15]. The wavenumber of the two peaks are plotted against temperature in Fig.…”

Design of Oligo(ethylene glycol)-Based Thermoresponsive Polymers: an Optimization Study

“…For instance, oligo(ethylene glycol)-grafted polymers based on poly(vinyl ether) [14,15], polynorbornene [16], polyester [17], polystyrene [18,19], polyacrylate [20][21][22], or polymethacrylate [23][24][25][26] backbones were all reported to exhibit a LCST in water. This thermoresponsive behavior is believed to be related to the amphiphilic character of these polymers [27,28]. Indeed, the hydrophilic oligo(ethylene glycol) side-chains form H-bonds with water, whereas the backbones, which are usually less polar in nature, lead to a competitive hydrophobic effect.…”

Synthesis and Properties of Novel Thermoresponsive Polyesters with Oligo(ethylene glycol) Pendent Chains

“…This fact can be explained by the phase transition mechanism qualitatively, according to polymethacrylate with oligo-EG side chain system. [ 22 ] For a given macromolecular chain, a constant time is needed to finish the phase transition. Thus, the faster heating rate will lead to the shift of transition temperature to a higher value, but with an unchanged LCST transition curve.…”