2414 refractive index detector ri

GPC-MALLS (Wyatt Technology Corporation, Santa barbara, CA, USA) was employed for evaluating the distributions of molecular weight and mass of UPF. This system employs a Waters 2690D separations module, a Waters 2414 refractive index detector (RI) and a Wyatt DAWN EOS MALLS detector. Ten milligrams of UPF was dissolved in 1 mL of 0.1 M NaNO₃ solution that was rolled overnight so that the entire amount was dissolved. Post a four-fold dilution, a 0.45 μm nylon filter (Millipore Corp., Billerica, MA, USA) was utilized to filter the solution of which 100μL was injected. A series of OHpak SB-805 HQ, OHpak SB-806 HQ, and OHpak SB-803 HQ columns were used. The collection and analysis of data was done using Astra 4.90.08 software (Wyatt Technology Corporation, Santa barbara, CA, USA).

¹H nuclear magnetic resonance (¹H NMR) spectra were recorded with a Mercury VX-300 spectrometer (300 MHz, Varian, Palo Alto, CA, USA). Fourier transformed infrared (FTIR) spectra were recorded on a Nicolet 6700 (Thermo Fisher, Hampton, NH, USA). The molecular weights and the molecular weight distributions of the obtained mPEG-PAAHPs were evaluated by size-exclusion chromatography-multi angle light scattering (SEC-MALLS, Milford, MA, USA) system consisted of a Waters 2690D separations module, a Waters 2414 refractive index detector (RI) and a Wyatt DAWN EOS MALLS detector. DMF containing 10 mM LiBr was used as the mobile phase at a flow rate of 0.3 mL/min at 30 °C. The data were processed with Astra software (Wyatt Technology, Santa Barbara, CA, USA).
Temperature responsive behaviors of mPEG-PAAHPs were evaluated by a transmittance measurement at 500 nm (Perkin-Elmer Lambda Bio 40 UV/Vis spectrometer, Hebron, KY, USA) and dynamic light scattering (DLS) (Nano ZS ZEN3600, Malvern Instruments, Westborough, MA, USA). The morphology of the nanoparticles was determined by DLS with a fixed scattering angle of 173° and by transmission electron microscopy (TEM). In this study, the cloud point (CP) was defined as the temperature corresponding to a 10% reduction in the initial transmittance of the solution.