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

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).

Domain Structure, Thermal and Mechanical Properties of Polycaprolactone-Based Multiblock Polyurethane-Ureas under Control of Hard and Soft Segment Lengths

“…SS are represented by long-chain diols, and their T g is much lower than room temperature. The different nature of thermodynamically incompatible blocks leads to their microsegregation and the formation of a domain structure [ 6 , 7 , 8 , 9 , 10 ]. Ordered areas of block structure (domains) in PU can be formed both due to the stacking of hard segments through intermolecular interactions, and as a result of mutual orientation of soft polyesters, if they are of sufficient length.…”

Towards high-performance polyurethanes: a mechanism of amine catalyzed aromatic imide formation from the reaction of isocyanates with anhydrides

“…[6][7][8][9][10][11][12][13] They have been used to improve the properties of a variety of polymer matrixes (e.g., poly(ether imide)s, poly(ester imide)s, poly(amide imide) s). 10,[14][15][16][17][18] Especially the co-polymerization of prepolymers containing aromatic polyimide structures with conventional PU raw materials results in significant improvements in thermal stability and flame retardancy and hence, poly(urethane imide) s are promising building blocks for the development of new thermoplastics, [19][20][21][22][23][24][25] rigid foams [26][27][28][29][30] and coatings. [31][32][33][34] Aromatic imides are usually introduced in poly(urethaneimide)s by the reaction of amines or isocyanates with anhydrides.…”

“…, poly(ether imide)s, poly(ester imide)s, poly(amide imide)s). 10,14–18 Especially the co-polymerization of prepolymers containing aromatic polyimide structures with conventional PU raw materials results in significant improvements in thermal stability and flame retardancy and hence, poly(urethane imide)s are promising building blocks for the development of new thermoplastics, 19–25 rigid foams 26–30 and coatings. 31–34…”

Solvent-Free Preparation of Thermally Stable Poly(urethane-imide) Elastomers

“…With the fast development of the PU market, further improvement of the chemical and physical properties of PU materials will make them meet the increasing demands on high-performance materials and suit a rising number of applications. This can be achieved by the chemical modification of PU with thermally stable chemical motifs such as aromatic polyimides, which are one of the most remarkable structures with respect to their outstanding thermal, mechanical, and electrical properties. − As aromatic polyimides have been used to enhance the thermal properties of various polymer matrices, such as poly­(ether imide)­s, poly­(ester imide)­s, and poly­(amide imide)­s, ,− the incorporation of aromatic polyimides in PU promises the development of thermoplastics, − rigid foams, − and coatings − with significantly enhanced thermal stability and flame retardancy, which is especially important for construction and automotive industries.…”