کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5180092 1502533 2015 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Dual thermo- and light-responsive nanorods from self-assembly of the 4-propoxyazobenzene-terminated poly(N-isopropylacrylamide) in aqueous solution
موضوعات مرتبط
مهندسی و علوم پایه شیمی شیمی آلی
پیش نمایش صفحه اول مقاله
Dual thermo- and light-responsive nanorods from self-assembly of the 4-propoxyazobenzene-terminated poly(N-isopropylacrylamide) in aqueous solution
چکیده انگلیسی


- LCST for the 4-propoxyazobenzene-terminated PNIPAM solution clearly decreased after UV irradiation, and the repeated LCST difference depended on both Mn and amount of azobenzene chromophore.
- The PNIPAM solution could self-assemble into nano-micelles with 4-propoxyazobenzene as the hydrophobic cores and PNIPAM chains as the hydrophilic shells.
- After UV irradiation, the unstable spherical micelles transformed to metastable nanorods, then to longer rods, and finally to flake-like particles by heating.

Both temperature and light stimuli-responsive 4-propoxyazobenzene-terminated poly(N-isopropylacrylamide)s (PNIPAMs) were successfully synthesized by the atom transfer radical polymerization (ATRP) of NIPAM. 1H NMR and UV-vis absorption spectra indicated rapid photoisomerization rate of 4-propoxyazobenzene moiety. Interestingly, the lower critical solution temperature (LCST) for PNIPAM aqueous solution clearly decreased after UV irradiation, and the repeated LCST difference (ΔTmaxy = 5 °C) depended on both the number-average molecular weight and amount of azobenzene chromophore. Dynamic light scattering (DLS) and static light scattering (SLS) measurements showed that the PNIPAM aqueous solution could self-assemble into nano-micelles with 4-propoxyazobenzene as the hydrophobic cores and PNIPAM chains as the hydrophilic shells. UV irradiation induced the increase of particle size due to the formation of much looser cores of cis-azobenzene. TEM images showed the presence of both nanorods and spherical micelles. After UV irradiation, the unstable spherical micelles transformed to metastable nanorods, then to longer rods, and finally the longer rods began to transform to flake-like particles via horizontal inter-rod aggregation above LCST.

After UV irradiation, the unstable spherical micelles from 4-propoxyazobenzene-terminated poly(N-isopropylacrylamide) transformed to metastable nanorods, then to longer rods, and finally to flake-like particles via horizontal inter-rod aggregation by heating, which led to the LCST downshift.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Polymer - Volume 73, 2 September 2015, Pages 195-204
نویسندگان
, , , , , , ,