Synthesis of thermo‐responsive 4‐arm star‐shaped porphyrin‐centered poly(N,N‐diethylacrylamide) via reversible addition‐fragmentation chain transfer radical polymerization

Abstract

Tetrafunctional porphyrins-containing trithiocarbonate groups were synthesized by an ordinary esterification method. This tetrafunctional porphyrin (TPP-CTA) could be used as a chain transfer agent in a controlled reversible addition-fragmentation chain transfer (RAFT) radical polymerization to prepare well-defined 4arm star-shaped polymers. N,N-Diethylacrylamide was polymerized using TPP-CTA in 1,4-dioxane. Poly(N,N-diethylacrylamide) (PDEA) is known to be a thermo-responsive polymer, and exhibits a lower critical solution temperature (LCST) in water. The star-shaped PDEA polymer (TPP-PDEA) was therefore also thermo-responsive, as expected. The LCST of this polymer depended on its concentration in water, as confirmed by turbidity, dynamic light scattering (DLS), static light scattering (SLS), and 1 H NMR measurements. The porphyrin cores were compartmentalized in PDEA shells in aqueous media. Below the LCST, the fluorescence intensity of TPP-PDEA was about six times larger than that of a water-soluble low molecular weight porphyrin compound (TSPP), whose fluorescence intensity was independent of temperature. Above the LCST, the fluorescence intensity of TPP-PDEA decreased, while the intensity was about three times higher than that of TSPP. These observations suggested that interpolymer aggregation occurred due to the hydrophobic interactions of the dehydrated PDEA arm chains above the LCST, with self-quenching of the porphyrin moieties arising from these interactions.

Synthesis of porphyrinic polystyrenes and their self-assembly with pristine fullerene (C60)

“…The fluorescence intensity of porphyrin was gradually quenched with the addition of C 60 toluene solution. On quantitative basis, the binding constant, 1.33 Â 10 4 M À 1 was calculated from Stern-Volmer plot [25] of emission data, inset of Fig. 1(B).…”

“…S-1-dodecyl-S-(a,a-dimethyl-a -acetic acid) trithiocarbonate (DDAT) was easily synthesized by the reported method [25]. DDAT was then coupled with THPP in DCM to give TPP-DDAT (Scheme S1).…”

Self-assembly of multi-responsive poly(N-isopropylacrylamide)-b-poly(N,N-dimethylaminopropylacrylamide) in aqueous media

“…2,2 0 -Azobis (isobutyronitrile) (AIBN, 98.0%) from Wako Pure Chemical Industries Ltd. (Osaka, Japan) was recrystallized from methanol. a-Methyl trithiocarbonate-S-phenylacetic acid (MTPA) was synthesized by the method reported previously [38]. N,N-dimethylaminopropyl acrylamide (DMPA, 99.6%) was a gift from Kohjin Co., Ltd. and was passed through an inhibitor-remover column.…”

Photo-induced in situ crosslinking of polymer brushes with dimethyl maleimide moieties for dynamically stimulating stem cell differentiation

“…We used α-methyltrithiocarbonate-S-phenylacetic acid (MTPA) as a chain transfer agent (CTA) for reversible addition fragmentation chain transfer (RAFT) polymerization and 2-(3,4-dimethyl-2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-ethyl methacrylate (dimethylmaleimide ethylmethacrylate; DMIMA) as a photo-crosslinker, for synthesis, similarly to previous research [10,12]. The substrate grafting photo-crosslinkable polymer brush was prepared by si-RAFT polymerization as follows ( Figure 2).…”