I 200 300 400 500 600 h (nm) Fig. 5. UV-vis absorption spectra of an aqueous solution of 1 containing 1.4 M LiC104 at room temperature and above the LCST.
Experimental
Polysilane 1 was prepared according to literature procedures [2,4]. For all measurements, 1 was used at a concentration of 0.40 mM. Variable-temperature solution UV spectra were obtained with a Cary 5 UV-vis-NIR spectrophotomcter (solvents: either spectrophotometric grade THF or water). A home-built. closed sample compartment equipped with a gas and a cooling inlet and outlet, a brass cuvette holder, and quartz windows was used for temperature-dependent measurements. Fluorescence spectra were obtained on a Spex Fluorolog apparatus. Static light-scattering experiments were performed on a FICA SO spectrometer (i = 546 nm). Scattering angles varied from 30 to 150". Dynamic light scattering (DLS) was performed with a Krypton laser source (200 mW, Spectra Physics 2020) at 2. = 647 nm under vacuum with scattering angles varying from 15 to 120". Measured DLS correlation functions (Malvern 7032 CE correlator) were fit to a second order cumulant expression of the usual exponential decay function."'] With both scattering techniques the scattering cell was thermostated and index matched using a toluene bath. Temperatures were close to the onset of the LCST. At T 2 70 "C, multiple scattering occurred due to the enhanced turbidity of the samples.