American Chemical Society
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High-Barrier Poly(hydroxy amide ethers):  Effect of Polymer Structure on Oxygen Transmission Rates. 3

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journal contribution
posted on 1998-10-30, 00:00 authored by David J. Brennan, Jerry E. White, Charles N. Brown
The synthesis of a series of new high-barrier poly(hydroxy amide ethers) is described. The polymers are formed by the reactions of aromatic diglycidyl ethers, with N,N‘-bis(3-hydroxyphenyl)adipamide, HOC6H4NHCO(CH2)4CONHC6H4OH, at 140−160 °C in propylene glycol monophenyl ether solvent using ethyltriphenylphosphonium acetate as initiator. Poly(hydroxy amide ethers) of general structure [−CH2CH(OH)CH2OArOCH2CH(OH)CH2OC6H4NHCO(CH2)4CONHC6H4O−]n are readily prepared in high molecular weight. The mainly amorphous thermoplastics have glass transition temperatures (Tg) of 78−146 °C and oxygen transmission rates (O2TR) that range from 0.2 to 1.8 cc·mil/(100 in.·atm·day) (barrier units or BU) at 23 °C and 45−90% relative humidity. It was determined that barrier properties improve (i.e., O2TR decreases) as the aromatic core unit, Ar, becomes less bulky or more polar. For example, the poly(hydroxy amide ether) in which Ar is the aromatic unit based on 2,2-bis(4-hydroxyphenyl)-1,1,1,3,3,3-hexafluoropropane has an O2TR of 1.8 BU, while the poly(hydroxy amide ethers) in which Ar is based on the more compact 2,6-dihydroxynaphthylene or more polar 1,1-bis(4-hydroxyphenyl)acetamide units have lower O2TR of 0.2 BU. In one instance, an amorphous poly(hydroxy amide ether) was induced to crystallize, yielding a semicrystalline polymer with significantly lower O2TR. The derivative in which Ar is the 4,4‘-biphenylene unit (O2TR = 0.3 BU, Tg = 110 °C) was annealed at 160 °C to yield a crystalline material with significant improvement in oxygen barrier (O2TR = 0.06 BU, Tg = 117 °C, Tm = 195 °C). Other effects that polymer structure has on O2TR and Tg are discussed.