Simultaneous small-angle neutron scattering and Fourier transform infrared spectroscopic measurements on cocrystals of syndiotactic polystyrene with polyethylene glycol dimethyl ethers

Abstract

Syndiotactic polystyrene (sPS) is a crystalline polymer which has a unique property; it is able to form cocrystals with a wide range of chemical compounds, in which the guest molecules are confined in the vacancies of the host sPS crystalline region. Recently, it has been found that even polyethylene glycol oligomers with a molecular weight of more than several hundreds can be introduced into the sPS crystalline region. It is quite important to know how such a long-chain molecule is stored in the host sPS lattice. To tackle this issue, a new simultaneous measurement method combing small-angle neutron scattering and Fourier transform infrared spectroscopy (SANS/FTIR), which has been recently developed by the authors, was applied to an sPS cocrystal with polyethylene glycol dimethyl ether with a molecular weight of 500 (PEGDME500). The temperature-dependent changes of the SANS profile and FTIR spectrum were followed from room temperature up to 413 K for a one-dimensionally oriented SANS/PEGDME500 cocrystal sample. The intensity of the reflections due to the stacking of crystalline lamellae showed a significant temperature dependence. The two-dimensional pattern in the high Q region of SANS also changed depending on temperature. The combined information obtained by SANS and FTIR suggested that PEGDME500 molecules are distributed in both the crystalline and amorphous regions in the low-temperature region close to room temperature, but they are predominantly included in the amorphous region in the high-temperature region. It was also suggested by the two-dimensional SANS profile that PEGDME500 molecules in the crystalline region have an elongated structure along the thickness direction of the crystalline lamellae.

Chemical Stabilization of Hexanal Molecules by Inclusion as Guests of Nanoporous-Crystalline Syndiotactic Polystyrene Crystals

“…A controlled release of active guests from cocrystalline polymer phases has been described in the literature. − These cocrystalline phases are obtained by absorption of active molecules in nanoporous-crystalline phases (exhibiting a density definitely lower than for the corresponding amorphous phases) and are available for two commercial polymers: syndiotactic polystyrene (s-PS) − and poly­(2,6-dimethyl-1,4-phenylene) oxide. − The thermoplastic nature of these materials allows their easy processing to products suitable for several applications like films, − membranes, and foams as well as their easy recycling. As a consequence, a number of applications in the fields of pollution remediation, − gas sorption and separation, − sensorics, − and catalysis − for these inexpensive and reusable materials have been proposed.…”

Soft Matter Sample Environments for Time-Resolved Small Angle Neutron Scattering Experiments: A Review

“…In order to investigate how high a molecular weight of polyethylene glycol dimethyl ether (PEGDME) can be incorporated in the crystalline region of syndiotactic polystyrene, one requires both the structural information provided by neutron scattering and vibrational spectroscopy. This was done by combining Fourier Transform Infrared Spectroscopy (FTIR) with SANS [147,148]. Here one encounters the issue that the optimum sample thickness required by both techniques is not the same.…”

Simultaneous SANS/FTIR measurement system incorporating the ATR sampling method

“…We employed this methodology to study cocrystal systems of syndiotactic polystyrene (sPS), where sPS includes other chemical species as guest molecules in its crystalline region. This attempt allowed us to interpret the temperature-dependent SANS profiles in relation to the behavior of the guest molecules (Kaneko et al, 2016(Kaneko et al, , 2019. On the other hand, it has become clear that an essential issue needs to be addressed to apply this simultaneous SANS/FTIR measurement system to various targets.…”