Rotaxanation of Polyisoprene to Render it Soluble in Water

Abstract

Water-soluble polyisoprene polyrotaxanes based on cyclodextrins (CDs) were synthesized via rotaxa-polymerization for the first time in a single step in one pot. Hydrophilic β-CD derivatives were utilized to complex isoprene, which was copolymerized with bulky, hydrophilic comonomers that acted as stoppers. The effect of the CD derivatives, stoppers, initiators and monomer content on the yield, CD coverage, and solubility of the polymeric product were investigated. The best yield of water-soluble polymer was obtained for the stopper comonomer that consisted of poly(ethylene glycol) methyl ether methacrylate (PEG MA). The highest CD content (67 wt %) on the polyisoprene backbone was observed for randomly methylated β-CD (RAMEB) with a 1:1 molar ratio of isoprene to CD in the feed and for the thermal radical initiator VA-044. Excess isoprene over CD increases the yield of polyrotaxane but lowers its CD content and gives rise to partially insoluble byproducts. Polymer backbones (30 kDa) with high molar masses were achieved.

Single-step preparation of topological gels using vinyl-modified β-cyclodextrin as a figure-of-six cross-linker

“…In this report, we have attempted to prepare topological gels in a single-step fashion using simultaneous free radical polymerization of isoprene and vinyl modified β-CyD (V-β-CyD) (Scheme 1). We expected that the obtained copolymer would append β-CyD moieties, and that the appended β-CyD can include another copolymer chain because the polyisoprene component acts as a guest for β-CyD [9][10][11][12]. In the expected structure ( Fig.…”

“…In the obtained polyrotaxane, the isoprene components of the copolymer were covered with methylated β-CyD, and the styrene components of the copolymer acted as a stopper to avoid dethreading of the methylated β-CyD. They have described this type of polymerization as rotaxa-polymerization [9][10][11]. Additionally, they demonstrated the applicability of many kinds of vinyl monomers and CyD derivatives in rotaxa-polymerization and showed a broad lineup of polyrotaxanes.…”

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

“…Recently our group has developed a method for a simple and environmentally friendly synthesis of polyrotaxanes. This, so called rotaxa -polymerization, is an aqueous, free radical copolymerization of a hydrophobic monomer, complexed in a host, with a stopper comonomer [ 24 – 25 ]. This latter has to be large enough to prevent the dissociation of the growing axis and the host, as it happens in the case of aqueous CD assisted homopolymerizations of hydrophobic monomers [ 26 – 28 ] including dienes [ 29 ].…”

“…Other benefits of trithiocarbonate CTAs are the good hydrolytic stability [ 38 ], as well as their approved application in controlled isoprene polymerization [ 39 – 40 ]. Randomly methylated β-CD (RAMEB) was chosen as the CD derivative for this polyrotaxane synthesis since it is highly water-soluble and provides a sufficiently high binding constant for isoprene [ 24 – 25 ].…”

Superstructures with cyclodextrins: Chemistry and applications IV

“…Well-defined fluorescent polyrotaxanes with alternating, threaded cucurbit[6]uril and CD rings were assembled by Fraser Stoddart’s group via an alkyne–azide click reaction exploiting supramolecular catalysis [ 23 – 24 ]. The concurrent radical copolymerization of 1,3-dienes and bulky stoppers in the presence of CDs (so-called rotaxa -polymerization) was further applied for the syntheses of water-soluble polyisoprene polyrotaxanes [ 25 ]. Furthermore, ABA-type block-copolyrotaxanes could be synthesized using this polymerization technique controlled by RAFT chain transfer agents [ 26 ].…”