High-efficiency synthesis of well-defined cyclic poly(N-vinylcaprolactam) and its solution properties

• Published in: Polymer (Guilford) Vol. 68; pp. 213 - 220
• Main Authors: Yang, Yaozong, Tang, Gang, Hu, Minqi, Shao, Lidong, Li, Jie, Bi, Yunmei
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 26.06.2015
• Subjects: Cyclic poly(N-vinylcaprolactam); Fluorescence; Light scattering; Nuclei; Polymerization; Precursors; Self assembly; Substitution reactions; Supramolecular self-assembly; Thermoresponsive phase transition behavior; Turbidity; Supramolecular self-assembly; Thermoresponsive phase transition behavior; Cyclic poly(N-vinylcaprolactam)
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2015.05.027

Well-defined cyclic poly(N-vinylcaprolactam) (c-PNVCL) was successfully synthesized by a combination of atom transfer radical polymerization (ATRP), supramolecular self-assembly and “selective” click cyclization at a relatively high concentration (10 mg/mL). α-Alkyne-ω-chloro heterodifunctional PNVCL precursor (l-PNVCL-Cl) was synthesized by ATRP of N-vinylcaprolactam (NVCL), followed by its conversion to α-alkyne-ω-azido heterodifunctional PNVCL (l-PNVCL-N3) via nucleophilic substitution reaction with NaN3. The intramolecular cyclization of l-PNVCL-N3 by “selective” click reaction in aqueous micellar media afforded well-defined and narrow-disperse c-PNVCL (PDI = 1.11). The target polymer and intermediates were characterized by GPC/MALLS, 1H NMR, and FT-IR. The thermoresponsive property of c-PNVCL and its linear precursor (l-PNVCL-N3) was studied and compared by turbidity and dynamic light scattering (DLS) measurements, and furthermore, their self-assembly behavior was investigated by fluorescence spectroscopy and transmission electron microscopy (TEM). Cyclic poly(N-vinylcaprolactam) can self-assemble to form smaller spherical micelles in aqueous solution and possesses lower critical solution temperature (LCST) and narrower thermal phase transition range in comparison with its linear analogue. [Display omitted] •Cyclic poly(N-vinylcaprolactam) (PNVCL) is prepared at a concentration of 10 mg/mL.•Cyclic PNVCL can be synthesized by “selective” click cyclization in micellar media.•Cyclic PNVCL tends to form smaller aggregates compared to its linear analogue.•Cyclic PNVCL possesses lower LCST compared to its linear analogue.•Cyclic PNVCL possesses narrower thermal phase transition range.