Segmented polyurethanes with 4,4′‐bis‐(6‐hydroxyhexoxy) biphenyl as chain extender. I. Synthesis and characterization of 2,4‐tdi‐polyurethanes

Abstract

SYNPOSISPolyurethanes composed of 2,4-toluene diisocyanate (TDI), poly(buty1ene adipate) diols (PBA) of different molecular weights, and 4,4'-bis-(6-hydroxyhexoxy)biphenyl (BHHBP) were prepared by a two-step solution polymerization process. The polyurethanes were characterized by elemental analysis, NMR, and SEC. The thermal properties were investigated by DSC, DMA, and optical polarizing microscopy. Dependent on the molecular weight of the PBA, a shift in the glass transition temperature Tg of the polyurethanes has been observed by DSC and DMA. Polyurethanes based on poly(buty1ene adipate)s of M , -2000 exhibited a Tg nearly independent on the hard-segment content up to 50% LC hard segments, indicating the existence of mainly phase separated soft and hard segments. By shortening the PBA chain length up to 1,000 and further to 600, the TB of the polyester soft-segment phase increases with growing hard-segment content, a consequence of enhanced interaction between the hard and soft segments. This tendency is observed to the greatest extent at polyurethanes with the shortest polyester diol and can be interpreted as a partial miscibility or compatibility of hard and soft segments. Although in polyurethanes with PBA 2000 the mesophase can be proven at a hard-segment content of -40%, its appearance in polyurethanes prepared with PBA 1000 or PBA 600 requires a hard-segment content > 60%. 0 1995 John Wiley & Sons, Inc.

Segmented polyurethanes with 4,4?-bis-(6-hydroxyhexoxy)biphenyl as chain extender. Part 2. Synthesis and properties of MDI-polyurethanes in comparison with 2,4-TDI-polyurethanes

“…1. The polymer was precipitated in methanol and extracted in a Soxhlet extractor for 5 h using acetone as the solvent.…”

“…In Part 1 we reported on segmented liquid-crystalline polyurethanes (LC-PUR) composed of poly-(butylene adipate)s (PBA) of different molecular weights, 2,4-toluene diisocyanate (2,, and the mesogenic diol 4,4'-bis-(6-hydroxyhexoxy)biphenyl (BHHBP) as the chain extender.…”

The influence of 4,4’-bis(6-hydroxyhexoxy)biphenyl moieties on properties of polyurethanes based on 4,4’-methylenebis(cyclohexyl isocyanate)

“…Penczek and co-workers investigated the influence of a 4,4'-bis(2-hydroxyethoxy)biphenyl (BH2) amount [8] and a high molecular diol length [9] on segmented PUs properties and microphase structure. PUs from BHn and other aromatic diisocyanates [3,5,6,[11][12][13] and aliphatic diisocyanates [2,5,11,13,14] were reported as well. Sun and Chang [13] described segmented PUs from 4,4'-bis(3-hydroxypropyloxy)biphenyl (BH3), poly(oxytetramethylene)glycol and 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI).…”

“…In recent years considerable attention has been paid on the structure -property relationships of polyurethanes (PUs) based on 4,4'-bis(ω-hydroxyalkoxy)biphenyls (BHn) [1][2][3][4][5][6][7][8][9][10][11][12][13]. Some PUs based on BHn are thermoplasts due to relatively low melting point of polymers in which macromolecules contain only short rigid mesogenic 4,4'-bis(oxy)biphenyl moieties.…”

“…Some PUs based on BHn are thermoplasts due to relatively low melting point of polymers in which macromolecules contain only short rigid mesogenic 4,4'-bis(oxy)biphenyl moieties. Both non segmented [1][2][3][4][5][6][7] and block [8][9][10][11][12][13][14] polymers have been described. Intensive work was focused on PUs based on tolylene 2,4-diisocyanate (TDI) [1][2][3][4][8][9][10][11].…”