ECB-ART-47130Polymers (Basel) 2016 Nov 11;811:. doi: 10.3390/polym8110367.
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Synthesis of Novel Temperature- and pH-Sensitive ABA Triblock Copolymers P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA): Micellization, Sol⁻Gel Transitions, and Sustained BSA Release.
Novel temperature- and pH-responsive ABA-type triblock copolymers, P(DEAEMA-co-MEO₂MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO₂MA-co-OEGMA), composed of a poly(ethylene glycol) (PEG) middle block and temperature- and pH-sensitive outer blocks, were synthesized by atom transfer radical polymerization (ATRP). The composition and structure of the copolymer were characterized by ¹H NMR and gel permeation chromatography (GPC). The temperature- and pH-sensitivity, micellization, and the sol⁻gel transitions of the triblock copolymers in aqueous solutions were studied using transmittance measurements, surface tension, viscosity, fluorescence probe technique, dynamic light scattering (DLS), zeta-potential measurements, and transmission electron microscopy (TEM). The lower critical solution temperature (LCST) of the triblock copolymer, which contains a small amount of a weak base group, (N,N-diethylamino) ethyl methacrylate (DEAEMA), can be tuned precisely and reversibly by changing the solution pH. When the copolymer concentration was sufficiently high, increasing temperature resulted in the free-flowing solution transformation into a micellar gel. The sol-to-gel transition temperature (Tsol⁻gel) in aqueous solution will continue to decrease as solution concentration increases.
PubMed ID: 30974672
PMC ID: PMC6431942
Article link: Polymers (Basel)
Genes referenced: eif3d
Article Images: [+] show captions
|Scheme 1. Schematic illustration of the synthesis of ABA triblock copolymer P(DEAEMA-co-MEO2MA-co-OEGMA)-b-PEG-b-P(DEAEMA-co-MEO2MA-co-OEGMA).|
|Figure 1. Transmittance curves of: (a) P1, P2, P3, P4 in aqueous solutions versus pH at 25 °C; (b) P2 in aqueous solution versus temperature at different pH; (c) P1, P2, P3, P4 in aqueous solutions versus temperature; and (d) P5, P2, P6, P7 in aqueous solutions versus temperature. (0.5 mg·mL−1).|
|Figure 2. Surface tension curve of P2 aqueous solution (0.5 mg·mL−1, pH 7) versus temperature.|
|Figure 3. Viscosity curves of 1 wt % P2 in aqueous solution versus temperature at different pH values.|
|Figure 4. Curves of the I3/I1 ratio of pyrene (Py) at 25 °C for various concentrations of P2 aqueous solution at pH 5, 7, and 10.|
|Figure 5. The aggregate particle diameters in P2 aqueous solution as a function of temperature (a) and solution pH (b) at 25 °C (0.5 mg·mL−1).|
|Figure 6. Zeta potentials of P2 aqueous solution (1.5 mg·mL−1) versus pH at 25 °C.|
|Figure 7. TEM images of micelles of P2 at 46 °C in acid medium (a) and basic medium (b).|
|Scheme 2. Micellization and gelation process of the ABA triblock copolymer.|
|Figure 8. The temperature induced sol–gel phase diagrams of P2 aqueous solution (a) and 30 mg·mL−1 P2 aqueous solution at different pH (b).|
|Figure 9. Photo of P2 aqueous solution at 25, 32, 37, 43, 65, and 75 °C (30 mg·mL−1, at pH 1.2, 7.4, and 11.8).|
|Figure 10. The cumulative release curves of bovine serum albumin (BSA) at different temperatures (a) and different pH (b).|
References [+] :
Determan, Supramolecular self-assembly of multiblock copolymers in aqueous solution. 2007, Pubmed