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Quantitative analysis of branching in poly(ortho ester) networks
Author(s) -
Shih Chung,
Waldron Niki,
Traugott Cathy
Publication year - 1993
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1993.070491218
Subject(s) - hydrolysis , branching (polymer chemistry) , chemistry , trimethylsilyl , polymer chemistry , polymer , isocyanate , covalent bond , molecule , triol , diol , polyurethane , organic chemistry
A direct method to quantify the branching attributable to fully reacted hexane‐1,2,6‐triol (HT) in poly(ortho ester) networks is reported. The method was based on the presence of free hydroxyl groups on incompletely reacted HT in the poly(ortho ester) matrix that were “tagged” prior to matrix hydrolysis. HT molecules that were completely reacted, i.e., acting as cross‐linker, within the polymer matrix would have no free hydroxyl groups available for “tagging” and posthydrolysis would be present as free HT. Experimentally, the matrix was swollen in p ‐dioxane, then phenyl isocyanate (PhCNO) was added to “tag” the hydroxyl groups in the presence of a stannous octoate catalyst. After removal of excess PhCNO, the matrix was hydrolyzed under mild acidic conditions. Any “untagged” HT was subsequently derivatized into trimethylsilyl ethers and analyzed by gas chromatography (GC). The level of branching determined by this direct chemical method correlated well with conventional swell ratio measurements. Furthermore, the extent of hydrolysis of the polymer backbone covalent bonds were also measured by this method since the resulting hydroxyl groups were “tagged” by PhCNO. All polyols were analyzed simultaneously by GC. Application of this method in characterization of the solid‐state hydrolysis of a poly(ortho ester) network was demonstrated. The degradation profiles of the branch sites and other backbone ortho ester bonds showed that the hydrolysis was initially slow, becoming progressively rapid. © 1993 John Wiley & Sons, Inc.