Synthesis, thermal, and mechanical characterization of liquid-crystalline polyhydroxyethers

Abstract

High molecular weight liquid-crystalline polyhydroxyethers, containing functional hydroxy groups, were synthesized from an aromatic diol and the diglycidylether of an aromatic diol. The polymers showed a liquid-crystalline melt when about 70% or more of the aromatic units in the chain were biphenyl units. Tensile modulus values varied from 3 GPa for as-cast films to 6 GPa for drawn films. These polymers are potentially suitable candidates to reinforce common thermoplastics by reactive blending. For this purpose polyhydroxyethers have been prepared, having a liquidcrystalline melt in the processing range of PET, viz. 260-290ЊC.

Influence of the type of polyhydroxyether on mechanical properties of PET/TLCP/polyhydroxyether blends

“…One of the polyhydroxyethers was prepared2 from 4,4′‐dihydroxy‐ α ‐methylstilbene and its diglycidyl ether. It will be referred to as α MS‐polyhydroxyether.…”

“…The improvement was achieved due to reactions taking place between the anhydride and secondary hydroxyl groups, which changes the rheological conditions (and possibly improves the adhesion between the phases). The results were obtained with a liquid crystalline polyhydroxyether based on 75 mol % biphenyl and 25 mol % phenyl units 2. In this article, two other types of polyhydroxyether were used in the PET/TLCP blend to establish Whether another mesogenic group in the polyhydroxyether has any effect on the improvement of the properties of the blend; for this purpose, a polyhydroxyether based on the α ‐methylstilbene unit was used, and Whether the liquid crystallinity of the polyhydroxyether is important in improving the blend properties.…”

Synthesis and improved mechanical properties of twin‐mesogenic epoxy thermosets using siloxane spacers with different lengths

“…LC epoxy thermosets contain rigid mesogenic groups in their backbone moiety of network chains, such as biphenyl, [9][10][11][12] stilbene, [13][14][15][16][17][18][19][20][21] azomethine, [22][23][24][25][26][27] ester, [28][29][30][31][32][33] azo, 34,35 and other, 36 which show excellent mechanical and thermal properties. LC epoxy thermosets contain rigid mesogenic groups in their backbone moiety of network chains, such as biphenyl, [9][10][11][12] stilbene, [13][14][15][16][17][18][19][20][21] azomethine, [22][23][24][25][26][27] ester, [28][29]…”

“…Several researchers have also reported that toughening of epoxy thermosets can be achieved using the liquid crystalline (LC) epoxy resins themselves without employing a modifier. LC epoxy thermosets contain rigid mesogenic groups in their backbone moiety of network chains, such as biphenyl, [9][10][11][12] stilbene, [13][14][15][16][17][18][19][20][21] azomethine, [22][23][24][25][26][27] ester, [28][29][30][31][32][33] azo, 34,35 and other, 36 which show excellent mechanical and thermal properties. In a series of previous studies, we reported a remarkable improvement in the fracture toughness of LC epoxy thermosets by increasing the LC domain size and the regularity of the LC phase structure.…”

Effect of backbone moiety in diglycidylether-terminated liquid crystalline epoxy on thermal conductivity of epoxy/alumina composite

“…In our previous report [1], the thermal conductivities of amorphous, crystalline, and LCE systems filled with Al 2 O 3 were investigated and the results clearly indicated that the thermal conductivity value of LCE composite is greater than those of crystalline and amorphous epoxies at the same Al 2 O 3 loading. A highly ordered structure is crucial for obtaining high thermal conductivity of composite by suppressing phonon scattering.It is known that LCE species bearing various mesogenic units in structure, such as azo [2,3], stilbene [4][5][6][7][8][9][10][11][12], biphenyl [13][14][15][16], binaphthyl [17,18], azine [19], ester [20][21][22][23][24][25], and azomethine [26][27][28][29][30], are widely used as thermosetting resins as well as liquid crystalline polymers. Many research groups have reported the synthesis, curing behavior, and mechanical properties of epoxy containing liquid crystalline structures, but only a few articles have been published on the thermal conductive property of LCE based on above mentioned mesogens.…”