Polyisobutylene RAFT CTA by a Click Chemistry Site Transformation Approach: Synthesis of Poly(isobutylene-b-N-isopropylacrylamide)

Abstract

A novel block copolymer, composed of polyisobutylene (PIB) and poly(N-isopropylacrylamide) (PNIPAM) segments, was synthesized. The PIB block was prepared via quasiliving cationic polymerization and end-functionalized by in-situ quenching to yield telechelic halogen-terminated PIB. Azido functionality was obtained by displacement of the terminal halogen through nucleophilic substitution, which was confirmed by both 1 H and 13 C NMR. Coupling of an alkyne-functional chain transfer agent (CTA) to azido PIB was successfully accomplished through a copper-catalyzed click reaction. Structure of the resulting PIB-based macro-CTA was verified with 1 H NMR, FTIR, and GPC, whereas coupling reaction kinetics were monitored by real-time variable temperature (VT) 1 H NMR. Subsequently, the function of this macro-CTA was demonstrated by RAFT polymerization of NIPAM for synthesis of the second block. RAFT kinetics was investigated under a variety of reaction conditions using VT NMR, and the resulting block copolymers were characterized by 1 H NMR and GPC. Aqueous solution properties were probed by dynamic light scattering confirming the presence of selfassembled aggregates with reversible temperature-sensitive responsiveness.

Dual Stimuli-Responsive Supramolecular Hydrogel Based on Hybrid Inclusion Complex (HIC)

“…When the temperature increases further, the radius of the micelles begins to decrease from 38 to 23 nm, which is attributed to further dehydration of the PNIPAM blocks. 28,29 The micelle structure has been observed by TEM ( Figure 3B), showing that the micelles are spherical with a radius ranging from 25 to 30 nm, which is consistent with the DLS results.…”

Graft copolymers of hydroxyethyl cellulose by a ‘grafting to’ method:15N labelling as a powerful characterisation tool in ‘click’ polymer chemistry

“…We chose RAFT polymerisation to prepare synthetic polymers because of its versatility in the range of monomers that are able to be polymerised in a controlled manner. Alkynecontaining chain transfer agents 30 suitable for preparing 'clickable' polymers from a range of monomers including Nvinyl-pyrrolidone, vinyl acetate, styrene and n-butyl acrylate [31][32][33][34][35] , were employed. N-vinylpyrrolidone (NVP) was chosen to exemplify our approach because it is a challenge to polymerise by other CRP methods, such as ATRP.…”

Polyisobutylene containing organic/inorganic hybrid block copolymers and their crystalline behavior

“…9), which showed birefringent texture before (70 o C) its melting and behave isotropically above (120 o C) its melting temperature. 42 Other block copolymers such as PIB 2k -b-PMAPOSS 5 and PIB 2k -b-PMAPOSS 22 showed similar behavior (Supporting Information Fig. S4).…”

“…9 It is interesting to note that, block copolymers shows T m that might be due to hydrophobichydrophobic interaction of both the block. 44 With increasing PMAPOSS block length, the T m decrease from 108.1 to 103.6 to 97.1 o C for PIB 2k -b-PMAPOSS 5 , PIB 2k -b-PMAPOSS 11 , and PIB 2k -b-PMAPOSS 22 , respectively. This result suggests that higher content of POSS moiety perturbs the ordered arrangement due to its bulkier alkyl substituent present on each corner.…”

“…Therefore, PIB based block copolymers have been prepared with radically polymerizable monomers using the combination of living cationic polymerization (LCP) and controlled radical polymerization (CRP) techniques such as atom transfer radical polymerization (ATRP). [18][19][20] Also, PIB segment was synthesized via LCP and end-functionalized with chain transfer agent (CTA) to prepare PIB-based macro-CTAs, which were used to make block copolymers via reversible addition-fragmentation transfer (RAFT) polymerizations with methyl methacrylate or styrene, 21 N-isopropylacrylamide, 22 and side-chain amino acid based methacrylate monomers. 23 To combine properties of PIB and POSS, well-defined PIBocta-arm radial star polymers with polysiloxane cores were produced from the reaction of allyl-terminated PIB and octa(hydrodimethylsiloxy)octasilsesquioxane.…”