Effect of Domain Structure of Segmented Poly(urethane-imide) Membranes with Polycaprolactone Soft Blocks on Dehydration of n-Propanol via Pervaporation.

Maria Sokolova,Erkki Lahderanta,Alexander Toikka,Alexander Bugrov,Alexander Smirnov,Valentin Svetlichnyi,Michael Smirnov

doi:10.3390/polym10111222

Abstract

Segmented poly(urethane-imide)s (PUIs) were synthesized by polyaddition reaction and applied for preparation of membranes. Tolylene-2,4-diisocyanate, pyromellitic dianhydride, and m-phenylenediamine for chain extension were used to form hard aromatic blocks. Polycaprolactone diols with molecular weights equal to 530 and 2000 g mol−1 were chosen as soft segments. The effect of the length of soft segments on the structure, morphology, and transport properties of segmented poly(urethane-imide) membranes were studied using atomic force microscopy, small-angle and wide-angle X-ray scattering, and pervaporation experiments. It was found that a copolymer with a shorter soft segment (530 g mol−1) consists of soft domains in a hard matrix, while the introduction of polycaprolactone blocks with higher molecular weight (2000 g mol−1) leads to the formation of hard domains in a soft matrix. Additionally, the introduction of hard segments prevents crystallization of polycaprolactone. Transport properties of membranes based on segmented PUIs containing soft segments of different length were tested for pervaporation of a model mixture of propanol/water with 20 wt % H2O content. It was found that a membrane based on segmented PUIs containing longer soft segments demonstrates higher flux (8.8 kg μm m−2 h−1) and selectivity (179) toward water in comparison with results for pure polycaprolactone reported in literature. The membrane based on segmented PUIs with 530 g mol−1 soft segment has a lower flux (5.1 kg μm m−2 h−1) and higher selectivity (437).

Highlights

Membranes based on segmented poly(urethane-imide)s with polycaprolactone soft segments of of different molecular weights (530 and 2000 g mol−1 ) were synthesized by a polyaddition reaction
Investigation with Atomic force microscopy (AFM) reveals that the copolymer with a shorter soft segment (530 g mol−1 ) consists
Investigation with AFM reveals that the copolymer with a shorter soft segment (530 g mol−1) consists of soft domains in a hard polymer matrix, while the introduction of PCL blocks with a molecular of soft domains in a hard polymer matrix, while the introduction of PCL blocks with a molecular weight equal to 2000 g mol−1 leads to the formation of hard domains in a soft matrix

Summary

Introduction

Polymers 2018, 10, 1222 candidates for application in such fields as fiber optics materials [3,4], microelectronics packaging materials [5], and membranes separation of industrially important gas [6,7] and liquid [8,9] mixtures. The dense structure and chemical resistivity lead to a lack of biodegradation, poor solubility and low permeability, which restricts the possible fields of PI application. In this sense, the synthesis of PI modified with extended soft aliphatic blocks, for example, polyesters, has recently attracted attention [10,11]. The thermodynamic incompatibility of PI and PCL blocks in such systems is preserved and promotes the formation of a domain structure [15]

Methods

Results

Conclusion