Synthesis and liquid-crystalline properties of thermotropic polyurethanes prepared from 1,4-diisocyanates and 4,4'-bis(.omega.-hydroxyalkoxy)biphenyls

Abstract

A new series of thermotropic polyurethanes was synthesized by reacting such para-substituted diisocyanate monomers as 2,5-tolylene diisocyanate (2,5-TDI) and 1,4-phenylene diisocyanate (1,4-PDI), with 4,4'-bis(oi-hydroxyalkoxy)biphenyls (BPm: HOCmH2mOC6H4C6H4OCmH2mOH; m is the carbon number of the hydroxyalkoxy group) in DMF. Intrinsic viscosities of the polymers were in the range of 0.41-0.99 dL/g. DSC thermograms for these polymers exhibited two endothermic peaks corresponding to phase transitions of melting and isotropization. Mesomorphic behavior of the polyurethanes was also observed under a polarizing microscope. For example, polyurethane 1,4-PDI/BP6 with [tj] = 0.77 prepared from 1,4-PDI and 4,4'-bis-[(6-hydroxyhexyl)oxy] biphenyl (BP6) exhibited a liquid crystalline phase from 247 to 259 °C. Infrared study indicated that the hydrogen bonding between urethane linkages affected the mesomorphism. Thermogravimetric analysis of 1,4-PDI/BPm showed that no weight loss of the polymer occurred up to 300 °C under an air atmosphere.

Synthesis and Thermotropic Properties of Polyurethanes Prepared from 2,5-Tolylene Diisocyanate and 2,6-Bis(ω-hydroxyalkoxy)naphthalenes

“…The peak at 1696 cm -1 was ascribed to the hydrogen bonded C=O peak. 12 • 21 • 22 The shoulder peak due to free carbonyl group was observed at 1732 cm -1 _ 12, 21,22 The thermal properties of these polymers were studied by DSC and polarizing microscopy. DSC thermograms of 2,5-TDI/BHN8 (A) and 2,5-TDI/BHNl l (B) in the 1st cooling and heating scan are shown in Figure 3.…”

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.…”

“…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]. 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.…”

Thermotropic Liquid-Crystalline Polymers Having Five-Membered Heterocycles as Mesogens V. Relationship between Polymer Structure and Thermotropic Liquid-Crystallinity in Semi-Rigid Polyesters Composed of Twin 2-Phenyl-1,3,4-thiadiazoles Having Central Aliphatic Chains

“…w,w'-(4,4'-Biphenylenedioxy)dialcohols (6a-d) were synthesized from 4,4'-dihydroxybiphenyl and w-halogenoalcohols in DMF in the presence of potassium carbonate according to the reported methods. [17][18][19][20][21][22] 753 …”