Polymerization of ethylene oxide with a calixarene‐based precursor: Synthesis of eight‐arm poly(ethylene oxide) stars by the core‐first methodology

Abstract

Eight-arm poly(ethylene oxide) (PEO) stars were prepared by the core-first method with a newly designed octahydroxylated precursor. This compound was readily obtained in two steps from commercially available tert-butylcalix [8]arene. The choice of the proper solvent of polymerization proved crucial to obtain PEO star materials with a narrow distribution of molar masses. For instance, the use of dimethyl sulfoxide (DMSO) resulted in PEO samples of rather large polydispersities (PDI: 1.3-1.5). In this solvent, the calixarene-based precursor was only sparingly soluble, and an attempt to metalate its eight hydroxyl groups produced insoluble alkoxides. In addition, the presence of a side population of low-molar-mass species attributable to linear chains was detected because of the chain transfer of propagating alkoxides to DMSO. Polymerization experiments carried out in tetrahydrofuran (THF) as solvent afforded better control over the molar masses and PDIs. This was related to the better solubility of the octafunctional calixarene-based precursor in THF and to the small tendency of the alkoxides formed to aggregate in that solvent. Under such conditions, all eight hydroxyl functions efficiently initiated the polymerization of ethylene oxide. In this way, well-defined PEO stars (PDI Ͻ 1.2) of tunable molar masses incorporating a calixarene-based core could be obtained, as it was supported by the characterization of the samples by size exclusion chromatography, NMR, and viscometry.

Multifunctional Poly(ethylene glycol)s

“…Innovative strategies developed in recent years to overcome the intrinsically low loading capacity of PEG have been dendronization of PEG [45,46] or the synthesis of star-or dendrimer-like PEGs. [39,[47][48][49][50] As in the case of block copolymers based on PEG combined with monomers other than epoxides, for example, N-carboxy anhydrides, either the polymer structure or the chemical composition are significantly different from the established PEG homopolymer. [51][52][53][54][55][56] Considering the desired features, it is surprising that both linear block and random copolymers of ethylene oxide (EO) and appropriate epoxide comonomers represent a rather neglected class of polymers.…”

Free‐radical polymerization of methyl methacrylate with a tetrafunctional peroxide initiator

“…An extensive amount of work has already been completed on the use of multifunctional initiators in controlled/living polymerizations such as atom transfer radical polymerization (ATRP),5–7 nitroxide‐mediated polymerization (NMP),8 reversible addition–fragmentation chain transfer polymerization (RAFT),9, 10 cationic polymerization,11–13 and anionic polymerization 14, 15. Recent reviews on the use of multifunctional initiators in controlled/living polymerizations include those written by Matyjaszewski (ATRP),16 Hawker et al (NMP),17 Barner et al (RAFT),18 Charleux and Faust (cationic),19 and Hadjichristidis et al (anionic) 20.…”

Syntheses and Refractive-Indices Properties of Novel Octa-Arms Star-Shaped Polysulfides Radiating from p-t-Butylcalix[8]arene Core

“…Calixarenes, such as p-t-butylcalix [8]arene (BCA), p-methylcalix [6]arene (MCA), and calix [4]resorcinarene (CRA), are cyclic oligomers with many hydroxy groups and can be used as the cores for the synthesis of star-shaped polymers. Furthermore, Sawamoto 27 and Taton 28 reported that the well-defined star shaped polymers with 4, 6, and 8-arms were prepared by the core-first methods using the calixarene derivatives as multifunctional initiators.…”