Thermoresponsive gels directly obtained via visible light-mediated polymerization-induced self-assembly with oxygen tolerance

Correction for ‘Thermoresponsive gels directly obtained via visible light-mediated polymerization-induced self-assembly with oxygen tolerance’ by Kaixuan Ren et al., Polym. Chem., 2017, DOI: 10.1039/c7py00558j.

(power: 5W, light intensity: 1.2 mW/cm 2 ).The reaction solution was irradiated by blue LED strips overnight (16 h) at 25 o C without deoxygenation, and the reaction was stopped by switching off the blue LED strips.For polymerization kinetics study, DMSO (10 μL) was added as an internal reference for 1 H NMR analysis.At predetermined time, aliquots were withdrawn and analyzed by 1 H NMR (methanol-d 4 ) and GPC to measure the monomer conversion, molecular weight and polydispersity index (PDI), respectively.

Characterization.
1 H NMR Spectroscopy. 1 H NMR spectra of PEG-b-PHPMA block copolymers in methanol-d 4 or D 2 O were recorded on an Agilent I500 NMR spectrometer.
Gel Permeation Chromatography (GPC).Number-average molecular weight (M n ), weightaverage molecular weight (M w ) and polydispersity index (PDI) of PEG-b-PHPMA block copolymers were determined by gel permeation chromatography (GPC) using an Agilent 1260 system equipped with a refractive index detector.The eluent was THF at a flow rate of 1.0 mL/min at 40 o C. Calibration curve was achieved by using a series of monodispersed polystyrene (PS) standards with a molecular weight ranging from 580 to 3.2×10 6 (Agilent Technologies).

Critical Micellar Concentration (CMC) Measurement.
The CMC of PEG 45 -TTC macro-CTA in water as well as in 5% HPMA aqueous solution was measured by fluorescent spectrometry with nile red as a probe.The PEG 45 -TTC macro-CTA was dissolved in H 2 O or 5% HPMA aqueous solution at a series of concentrations containing a predetermined amount of nile red.The concentration of PEG 45 -TTC macro-CTA ranged from 9.8×10 -4 to 5 mg/mL and the concentration of nile red was fixed at 0.04 mg/L.The samples were then excited at 555 nm and the corresponding emission spectra from 580 nm to 800 nm were recorded.The fluorescence intensity at 635 nm was plotted as a function of PEG 45 -TTC concentration to determine the CMC.

Rheology
Measurement.The rheological properties of the PEG-b-PHPMA hydrogels were measured on an ARES-G2 ANTON PAAR rheometer using a parallel plate (plate diameter = 25 mm, gap = 0.5 mm).Storage modulus (G'), loss modulus (G'') and loss tangent (tan δ) were measured as a function of temperature and strain to determine the critical gelation temperature (CGT) and gel strength.Oscillatory temperature ramp was performed between 15 o C and 40 o C at a strain of 1% and an angular frequency of 1 rad/s.Oscillatory amplitude sweep was carried out in the range of 0.05%-100% at a constant angular frequency of 1 rad/s and a constant temperature of 30 o C. The outer edge of the sample was sealed with a thin layer of silicon oil to prevent the evaporation of water.Dynamic Light Scattering (DLS).The PEG-b-PHPMA block copolymer solution was diluted 100-fold to generate 0.1% aqueous solution.The intensity-average hydrodynamic diameter was measured by using a Delsa TM Nano C Particle Size & Zeta Potential Analyzer (Bechman Coulter, Inc.) with a scattering angle at 165 o at different temperature.The hydrodynamic diameter was determined by intensity following the CONTIN method.Transmission Electron Microscopy (TEM).The PEG-b-PHPMA block copolymer solution (0.1%, 10 μL) was dropped onto a 400 Mesh Copper Grid with Ultrathin Carbon Film (TED PELLA, INC) and blotted with filter paper to remove excess solution.The grids were then dried overnight and observed by using a JEOL 2100 electron microscope at an acceleration voltage of