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Synthesis and Characterization of Long-Chain Branched Poly(ether imide)s with A3 Comonomers
journal contribution
posted on 2020-01-27, 21:44 authored by Joseph
M. Dennis, Ryan J. Mondschein, Josh D. Wolfgang, Maruti Hegde, Roy Odle, Timothy E. LongThe
synthesis of an aromatic trisamine enabled the generation of
long-chain branched poly(ether imide)s (LCB-PEIs). The nucleophilic
aromatic substitution of 1-chloro-4-nitrobenzene with 1,1,1-tris(4-hydroxyphenyl)ethane
resulted in tris((p-nitrophenoxy)phenyl)ethane,
and a subsequent reduction afforded tris((p-aminophenoxy)phenyl)ethane
(TAPE) in high yields (>90%). Introducing TAPE at low percentages
with m-phenylenediamine and bisphenol A dianhydride
enabled synthesis of high molecular weight, branched poly(ether imide)s
with varied branch lengths. The stoichiometric imbalance and phthalic
anhydride end-capping controlled molecular weights. Complementary 1H NMR spectroscopy and size exclusion chromatography (SEC)
identified average branch length as a function of TAPE incorporation
and provided comparisons in molecular weights and distributions. The
melt viscosity and thermal stability at elevated temperatures (∼340
°C) probed the feasibility of melt processing of LCB-PEIs in
comparison to linear analogues. At equivalent molecular weight and
below 1.5 mol % TAPE, melt viscosities increased at low shear rates.
However, increasing TAPE above 1.5 mol % decreased melt viscosities
at low shear rates, suggesting a correlation of branch length and
polydispersity with melt viscosity. Mechanical testing of injection-molded
samples demonstrated minimal changes in tensile and impact properties
with branching. The LCB-PEIs herein establish their potential role
in molding processes such as blow molding that requires high melt
strength and advantageous shear thinning.