Qm 40

The self-assemblies of polymer cross-linkers in a pre-gelled solution were investigated using a pyrene probe. [14 (link),15 (link)]. The pyrene (Sigma, Peabody, MA, USA) was dissolved in acetone to prepare a stock solution with a concentration of 6.0 × 10⁻⁴ M. Polymer cross-linker pre-gelled solutions were prepared in DI (deionized) water (2 mL) by poly(ethylene glycol) diacrylate of M_n 575 g/mol (PEGDA-575, Sigma) and M_w 3400 g/mol (PEGDA-3400, Sigma), respectively. In parallel, acrylate group-free poly(ethylene glycol) of M_n 3350 g/mol (PEGdiol, Sigma) were dissolved in DI water as a control. Then, the pyrene solution was dropped into the polymer solutions with varying polymer concentrations. The mixture of the polymer solution and pyrene was sonicated for 10 min to ensure dispersion of pyrene in the polymer solution. The mixture was further incubated at room temperature for at least 12 h in the dark, so the pyrene was preferentially associated with hydrophobic domains of polymers. The mixture loaded in a quartz cuvette was excited at a wavelength of 330 nm and a resulting emission spectrum was obtained using photo luminescence (QM40, Photon Technology International, HORIBA, Japan). The band-width was adjusted to 2.0 nm for both excitation and emission.

HRTEM images were obtained on JEM 3010 high resolution transmission electron microscope. Field-Emission Scanning Electron Microscope (Carl Zeiss, SUPRA 55VP) was used to obtain SEM images and EDS analysis. Emission spectra were obtained on QM-40 (Photon Technology International, Inc.). A micro-Raman system (JY-Horiba, LabRam 300) was utilized for Raman spectrum recording with the 514.5 nm laser line from a Ar ion laser (Melles Griot, 35-MAP-321) for Raman excitation. Fluorescence images were obtained on Olympus X81 microscope coupled to an Andor Luca^EMS 658 M camera. Zeta potential was measured on NanoPlus-1 (Particulate Systems).