This work aims to synthesize poly(N-isopropylacrylamide)-based microgels with sharp phase transition by introducing a specific secondary structure to achieve pulsatile drug release near body temperature. To achieve this, N-isopropylacrylamide (NiPAM) based microgels were synthesized by surfactant free-radical polymerization of NiPAM in the presence of polyalanine terminated α-methallyl poly(ethylene glycol) ether (HPEG-Ala x ) as a macro-comonomer and N,N 0 -methylene bisacrylamide (MBA) as a chemical crosslinker. A series of microgels were characterized by TEM, DLS, UV-Vis, 1 H NMR, and other analytical methods. The introduction of hydrophilic HPEG allows the volume phase transition temperature (VPTT) to move towards the body temperature, and α-helix structure confers a high deswelling ratio and response sensitivity to the microgel, overcoming the disadvantage of a broadened phase transition caused by hydrophilic monomers. The presence of HPEG-Ala x significantly improves the stability of the microgel in the electrolyte solution at high temperatures. The drug release of the microgels was investigated with the model drugs, hydrophilic DOX and hydrophobic curcumin, showing that the microgels can release hydrophilic drugs in a pulsatile mechanism.

Low-frequencypIioiion spectra in a-SiN, : H/Si lieteros tructures have hcen observed by iiicaiis o f Driflouin light srattcring. Mcasurcinent of the frcqiicncy shift on longitudiiid and transversc acoustic ~JIOIIOIIS as well as on surface phonons enabled us to extract acciiratcly two independcnt &$tic moduli: cI1 and c44 dcduced from phase veJocities of bulk acoustic inodcs and scattc:ring wavevcctor, within effective medium approxima tion.

The rigid-ion model with only eight or nine meaningful parameters is applied to calculate the dispersion relations of both ferroelectric and paraelectric phases in PbTiO3. Phonon frequencies and vibration mode at the zone center were obtained. The good agreement between our calculation and the previously mode with eighteen parameters is shown. A simple model for investigation of the soft modes is suggested.