Phase behaviour of mixtures of polyethylene glycol and polypropylene glycol: Influence of hydrogen bond clusters on the phase diagram

Abstract

The phase behaviour of a binary polymer blend of polyethylene glycol (PEG600) and polypropylene glycol (PPG1000) of low polydispersity was investigated. The coexistence curves of five different compositions, including the critical composition, were measured by differential refractometry. From the coexistence curves, the critical exponents of the order parameter could be determined. The order parameter of the coexistence curve of the critical composition was b ¼ 0.357, near to the Ising value. The measured coexistence curves for different compositions were different to each other and to the cloud point curve measured by small angle light scattering. These differences are explained by clusters built of intermolecular hydrogen bonds which lead to a broad effective molar mass distribution of the mixture. Two of the investigated mixtures, the mixture of critical composition (y PPG ¼ 0.46, y PPG : mass fraction of polypropylene glycol) and a mixture of non-critical composition (y PPG ¼ 0.365) were also measured by static and dynamic light scattering. The measurements were carried out in the homogeneous one-phase region (above the critical temperature T C ) and in the two-phase region in both coexisting phases. The light scattering measurements showed, additionally to the composition fluctuations due to the phase transition of demixing, a contribution of larger objects, which could be attributed to hydrogen bonded clusters. The size of these clusters was estimated to be 250 nm to 550 nm.

Competitive hydrogen bonding mechanisms underlying phase behavior of triple poly(N‐vinyl pyrrolidone)–poly(ethylene glycol)–poly(methacrylic acid‐co‐ethylacrylate) blends

“…One such favorable interaction is hydrogen bonding that has been reported for many polymer blends 3–7. Although a considerable amount of research work has been performed on the contribution of hydrogen bonding to the phase behavior of polymer blends,8–13 there is lack of mechanistic understanding of effects of hydrogen bonding on the phase state of polymer blends.…”

Phase behaviour of mixtures of polyethylene glycol and polypropylene glycol: Influence of hydrogen bond clusters on critical composition fluctuations

“…For low molecular PCCP liquids, an Ornstein-Zernike model based on the susceptibility leads to values of 0.01 < Gi < 0.04 for the Ginzburg number 18 whereas for polymer mixtures, the Ginzburg number is dependent on the degree of polymerisation. For symmetric polymer mixtures with a degree of polymerisation N, the Ginzburg number is inversely proportional to N. 15,16 In a preceding paper 19 we had thoroughly investigated the influence of hydrogen bonds on the phase diagram of PEG/ PPG mixtures. There we found clusters built by intermolecular hydrogen bonds leading to a higher '' effective molar mass '' and a larger '' effective polydispersity ''.…”

Composition fluctuations in a non-critical binary polymer blend studied by ultrasonic and light scattering experiments

“…For this mixture, there exist reliable data from static light scattering. 51 The correlation lengths of the critical mixture determined by these two methods are shown in the inset of Fig. 5 as a function of the reduced temperature.…”

“…This aspect will be the subject of further investigations. 49 It is interesting that the concentrations of the maxima of the coexistence curves are similar for the critical mixture (solid circles) and the non-critical mixture (open circles).…”

“…The attribution to hydrogen bond clusters is also confirmed by an investigation of mixtures of PEG600/PPG1000 of different compositions in the one-and two-phase region which showed a dependence of the process on the composition of the mixture. 49,51 The faster relaxation process is related to the composition fluctuations. This is justified by the power law dependence of the related diffusion coefficient (see Fig.…”