Degree of Branching of Highly Branched Polyurethanes Synthesized via the Oligomeric A₂ Plus B₃ Methodology

Abstract

Summary: The oligomeric A2 plus monomeric B3 synthetic methodology provided highly branched, poly(ether urethane)s based on TMP (B3) and isocyanate endcapped polyethers. 13C NMR spectroscopic assignments for the branched polyurethanes were verified using model urethane‐containing compounds based on TMP and a monofunctional isocyanate (either cyclohexyl or phenyl isocyanate (PI)). Derivatization of hydroxyl endgroups with trifluoroacetic anhydride enhanced the 13C NMR resolution in spectra for branched polyurethanes. The 13C NMR resonance for the linear unit exhibited a broad shoulder due to quaternary carbons that were attributed to cyclic species in the highly branched polyurethanes. The classical DB calculation revealed the efficiency of the B3 monomer for branching; however, an equation that incorporated the linear contribution of the A2 oligomer provided a more accurate DB for highly branched polyurethanes.SEC chromatograms for increasing addition of A2.magnified imageSEC chromatograms for increasing addition of A2.

Long‐Chain Hyperbranched Polymers: Synthesis, Properties, and Applications

“…Although LCHBPs now remain in a nascent stage when compared with well‐developed conventional HBPs with short subchains, many synthetic approaches have been developed . In situations where “living” or controlled polymerizations such as anionic polymerization, ring opening polymerization (ROP), nitroxide mediated polymerization (NMP), atom transfer radical polymerization (ATRP), or reversible addition‐fragmentation chain transfer (RAFT) polymerization are usually utilized to afford AB x ( x ≥ 2) or A x (B x , x ≥ 3) macromonomers bearing various reactive functional groups.…”

“…Similar to the AB x macromonomer strategy, the A 2 + B x approach was accordingly designed for synthesizing LCHBP, where at least one of the A 2 or B x building units should be macromonomer, or both (Figure ) . Given that a simple coupling reaction of an A 2 monomer and a B x monomer will produce an “AB x ‐1 ” type monomer, we can primarily regard this A 2 + B x copolymerization as “AB x ‐1 ”‐type strategy.…”

“…In order to synthesize LCHBPs, a variety of methodologies have been developed, although in most cases long‐chain AB x ( x ≥ 2) macromonomer building blocks are needed, analogous to that in preparing classical HBPs with small molecular AB x monomers, where the group A can react with the B group . Moreover, LCHBPs can also be easily afforded through certain copolymerizations by using high molecular weight macromonomers or small molecular monomers, or simultaneously both, as building blocks via A 2 + B x ( x ≥ 3) or AB + AB x ( x ≥ 2) copolymerization process . Additionally, the famous self‐condensing vinyl polymerization (SCVP) usually affording conventional HBPs with short subchains has been adjusted for the preparation of LCHBPs through copolymerization of the traditional small molecular inimer with an additional comonomer, or direct homopolymerization of a macroinimer …”

Dendritic Polymers Based on Urethane Chemistry – Syntheses and Applications

“…Investigations on the rheological behavior of a highly branched polyurethane system, based on H 12 MDI‐capped polyether diol as A 2 ‐compound and TMP as B 3 ‐unit, showed a strong decrease in viscosity of the highly branched system in comparison to a linear polymer 47. The degree of branching of these long soft segment containing polymers was determined to be between 30 and 50% by NMR‐measurements 48…”

Synthesis and characterization of isocyanate-functionalized hyperbranched polyurethane and its cocuring with benzoxazine

“…b, which are assigned to the quaternary carbon for the dendritic, linear, and terminal groups from TMP. As compared with model compounds that represent dendritic unit, linear unit, and terminal unit, respectively , DB value of HPU NCO is 35.2% determined with formula (1). It should be noted that the value below the predicted 50% for HBPs synthesized with the same molar ration of A 2 to B 3 .…”