The influence of the length of alkoxy side groups on the phase state of polydialkoxyphosphazenes

Abstract

Polydialkoxyphosphazenes with different substituents varying from methoxy up to octoxy which contain only minor amounts (below 0,l mol-%) of various defective units in their macromolecules were synthesized. It was shown that such polyphosphazenes with propoxy, butoxy and pentoxy side groups can exist in the mesomorphic state and that a defect content as low as about 2 mol-% prevents mesophase formation. In spite of high flexibility of the main chain, the polydialkoxyphosphazenes were found to gain the ability to crystallize only if the number of C atoms in the alkoxy substituents is higher than six.

Columnar mesophase behaviour of poly(dibutylsiloxane) and related copolymers containing polar substituents

“…144-150°C (<0,1 mm) ' ). I3C NMR (63 MHz): 6 = l19,51 (C4 '),26,[15][16][17][18][19][20][21][22][23][24][25][26]13,25,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]72 (C2,C3),20,31,19,54 (CT,C3'),15,55 (Cl,Cl'),13,68 (C4). a) Distillation of the apolar fraction yielded 12,7 g (60,9%) hexabutylcyclotrisiloxane (purity 99,7% GLC); b.p.…”

High temperature behavior of poly[bis(2,2,2-trifluoroethoxy)phosphazene]

“…Above T (l), the backbone chains of the mesophase are pseudo-hexagonally packed. Thermotropic behavior and the inter-chain separation between molecules are influenced by side group size and chemical nature 15,16,25,26) . Whenever PBFP is heated through T (l) it transforms into a chain extended 2D mesophase which upon cooling transforms into the 3D orthorhombic chain extended form that becomes highly crystalline 5) .…”

Influence of the length of side substituents on optical and electro-optical properties of polydialkoxyphosphazenes

“…A variation in the spatial shape of the monomer unit and a change in its sign of anisotropy with length ening of aliphatic side groups may be responsible for the phase behavior and morphological properties of a number of PDAOPs at m = 4-6 [4][5][6][7]. As was men tioned above, the shape of the monomer unit of PDAOP is characterized by the highest symmetry in the "critical" region of side chain lengths.…”

“…As was men tioned above, the shape of the monomer unit of PDAOP is characterized by the highest symmetry in the "critical" region of side chain lengths. Shape sym metry, which provides competitive opportunities for molecule packaging, may cause various kinds of rear rangements during sequential heating and cooling of polydihexoxyphosphazene and polydiheptoxyphosp hazene [4][5][6][7]. Moreover, the possibility of the alterna tive orientation of highly symmetric PDAOP chains in terms of the shape of their units in a melt may be responsible for the mesomorphic behavior of these polymers only in a certain side chain length range.…”

“…Studies devoted to polydialkyloxyphosphazenes (PDAOPs) (R = -O-(CH 2 ) х -CH 3 ) indicate that their physical properties are dependent on the lengths of side substit uents [1,3,[4][5][6][7]. Some properties change monotoni cally with side chain lengthening, whereas the other properties remain unaffected.…”