We report the synthesis and gradient stimuliresponsive
properties of cyclodextrin-overhanging hyperbranched
core-double-shell miktoarm architectures. A ionic
hyperbranched poly(b-cyclodextrin) (b-CD) core was firstly synthesized
via a convenient ‘‘A2þB3’’ approach. Double-layered
shell architectures, composed of poly(N-isopropyl acrylamide)
(PNIPAm) and poly(N,N-dimethylaminoethyl methacrylate)
(PDMAEMA) miktoarms as the outermost shell linked to poly(
N,N-diethylaminoethyl methacrylate) (PDEAEMA) homoarms
which form the inner shell, were obtained by a sequential
atom transfer radical polymerization (ATRP) and parallel click
chemistry from the modified hyperbranched poly(b-CD) macroinitiator.
The combined characterization by 1H NMR, 13C NMR,
1H-29Si heteronuclear multiple-bond correlation (HMBC), FTIR
and size exclusion chromatography/multiangle laser light scattering
(SEC/MALLS) confirms the remarkable hyperbranched
poly(b-CD) core and double-shell miktoarm architectures. The
gradient triple-stimuli-responsive properties of hyperbranched
core-double-shell miktoarm architectures and the corresponding
mechanisms were investigated by UV–vis spectrophotometer
and dynamic light scattering (DLS). Results show that this
polymer possesses three-stage phase transition behaviors. The
first-stage phase transition comes from the deprotonation of
PDEAEMA segments at pH 9–10 aqueous solution under room
temperature. The confined coil-globule conformation transition
of PNIPAm and PDMAEMA arms gives rise to the second-stage
hysteretic cophase transition between 38 and 44 C at pH 10.
The third-stage phase transition occurs above 44 C at pH ¼ 10
attributed to the confined secondary conformation transition of
partial PDMAEMA segments. This cyclodextrin-overhanging
hyperbranched core-double-shell miktoarm architectures are
expected to solve the problems of inadequate functionalities
from core layer and lacking multiresponsiveness for shell
layers existing in the dendritic core-multishell architectures.
