Hydroxyfunctional oxetane-inimers with varied polarity for the synthesis of hyperbranched polyether polyols via cationic ROP

Abstract

Synthesis and characterization of novel hydroxyl‐functionalized oxetane‐inimers with varied alkyl chain length—3‐hydroxymethyl‐3‐methoxymethyloxetane, 3‐hydroxymethyl‐3‐propoxymethyloxetane, and 3‐hexoxymethyl‐3‐hydroxymethyloxetane—is reported. Cationic ring‐opening polymerization of these latent, cyclic AB2‐monomers leads to hyperbranched (hb) polyether polyols with degrees of branching between 34 and 69%, confirmed by inverse‐gated (IG) 13C NMR spectroscopy. The hyperbranching polymerization yielded apparent molecular weights (Mn) ranging from 500 to 2500 g mol−1 (size exclusion chromatography). Remarkably, by copolymerization of 1,1,1‐tris(4‐hydroxyphenyl)ethane as a “focal” unit, polymerization under slow monomer addition conditions lead to higher apparent molecular weights up to 11,220 g mol−1. The end groups of the hb polymers were studied via matrix‐assisted laser desorption/ionization time of flight mass and NMR spectrometry. By varying the alkyl chain length, tailoring of the solubility and glass transition temperatures of the materials is possible. Potential applications range from macroinitiators with defined polarity to tailoring of surface properties of antifouling materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2850–2859

Aliphatic Polyethers: Classical Polymers for the 21st Century

“…Oxetanes exhibit a higher basicity (pK a (oxetane) = −2.02, pK a (oxirane) = −3.70) and lower ring strain (oxetane: 106 kJ mol −1 vs. oxirane: 112 kJ mol −1 ) than oxiranes, which leads to a more facile polymerization following the cationic mechanism in contrast to oxiranes which are polymerized predominantly via an anionic mechanism . However, insertion polymerization, anionic polymerization and free radical ring‐opening polymerization are reported in some cases.…”

“…The copolymerization of different monomers allows the adjustment of the T m over a broad temperature range . In Table only symmetric oxetanes are mentioned, however, also asymmetric oxetanes are accessible …”

“…The polymers are resistant to common organic solvents and are only soluble in concentrated sulfuric acid or pyridine. The copolymerization with different functional oxetanes or oxiranes enables the adjustment of the solubility and opens up new possible applications …”

Branched aliphatic polyesters by ring-opening (co)polymerization

“…The method of synthesis of hyperbranched polymers by the ROMBR (ring-opening multibranching polymerization) of "latent" AB 2 cyclic monomers is predominantly exploited A c c e p t e d M a n u s c r i p t 11 for hydroxyl-substituted cyclic ethers like 3-membered hydroxymethyloxiranes [24,[55][56][57][58][59][60][61][62][63] or 4-membered hydroxymethyloxetanes [64][65][66][67][68][69][70][71][72][73].…”

Synthesis and cationic ring‐opening polymerization of oxetane monomer containing five‐membered cyclic carbonate moiety via highly chemoselective addition of CO2

“…Moreover, oxetane derivatives are used as functional monomers that can be converted to various kinds of linear, branched, and crosslinked polyoxetanes via cationic ring‐opening polymerization using catalytic amounts of Lewis acids. For example, branched and hyperbranched polyoxetanes were synthesized from hydroxyl‐substituted oxetanes in the presence of catalytic boron trifluoride diethyl etherate (BF 3 ‐Et 2 O) or trifluoromethanesulfonic acid (TfOH) . The polyethylene glycol‐terminated amphiphilic hyperbranched polyoxetanes resulted in formation of self‐assembly structures such as vesicles and cylindrical micelles, which suggest potential applications as biomaterials .…”