Gelation of PEO−PLGA−PEO Triblock Copolymers Induced by Macroscopic Phase Separation

摘要: The gelation behavior of aqueous solutions poly(ethylene oxide-b-(DL-lactic acid-co-glycolic acid)-b-ethylene oxide) (PEO-PLGA-PEO) triblock copolymer containing short hydrophilic PEO end blocks is investigated using dynamic light scattering, rheology, small-angle neutron scattering (SANS), and differential scanning calorimetry (DSC). For polymer concentrations between 5 35 wt %, four distinct regions the turbidity change depending on temperature were observed. Interestingly, in turbid solution region, gel phase formed for above 14 % an extremely slow relaxation was detected. In fact, a power law, which takes into account dynamics percolation clusters, dominates correlation function. rheological measurements, local maximum G' observed at around turbidity. We further found that G" > highly dependent frequency state implying viscoelastic characteristics, quite different from general concepts gels, typically by micellar packing. SANS profiles showing multiple peaks sol rather than as well DSC exotherm gels can also serve evidence states. Based upon experimental data obtained present study, new mechanism induced macroscopic separation copolymers such PEO-PLGA-PEO proposed. effect type ofhydrophobic middle discussed.