Effects of Polymer and Salt Concentration on the Structure and Properties of Triblock Copolymer Coacervate Hydrogels
Effects of Polymer and Salt Concentration on the Structure and Properties of Triblock Copolymer Coacervate Hydrogels
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DOI：
10.1021/ma302299r
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发表时间：
2013-02-26
期刊：
影响因子：
5.5
通讯作者：
Tirrell, Matthew V.
中科院分区：
文献类型：
--
作者：
Krogstad, Daniel V.;Lynd, Nathaniel A.;Tirrell, Matthew V.
建立了由相反电荷的ABA三嵌段共聚物的二元水溶液形成的复合凝聚水凝胶的结构-性质关系。通过将聚[(烯丙基缩水甘油醚)-b-(环氧乙烷)-b-(烯丙基缩水甘油醚)]官能化，使其具有鸟粪官能团或磺酸盐官能团，合成了带电三嵌段共聚物。当这些相反电荷聚合物的水溶液(约5-40wt%)混合时，官能化嵌段之间的静电相互作用导致相反电荷的末端嵌段结合到由不带电荷的亲水性PEO中间嵌段连接的相分离的复杂凝聚结构域中。用小角X射线散射(SAXS)和动态力学光谱对所得结构进行了研究。凝聚结构域的结构对凝胶的粘弹性能有很大的影响，随着嵌段共聚物浓度的增加，随着混合物从无序的结构域阵列转变为有序的体心立方结构，水凝胶的储能模数显著增加。当聚合物浓度进一步增加到30wt%时，出现了六方结构，这与弹性模量下降了25%相吻合。进一步的结构变化，导致粘弹性反应的变化，也是由盐浓度的变化引起的。交联物的粘弹性和物理性质对这些凝胶作为注射给药系统的适用性具有重要意义。
Structure-property relationships were established for complex coacervate hydrogels formed from binary aqueous solutions of oppositely charged ABA triblock copolymers. The charged triblock copolymers were synthesized by functionalizing poly[(allyl glycidyl ether)-b-(ethylene oxide)-b-(allyl glycidyl ether)] with either guanidinium or sulfonate functional groups. When aqueous solutions (ca. 5-40 wt %) of these oppositely charged polymers were mixed, the electrostatic interactions of the functionalized blocks led to the association of the oppositely charged end-blocks into phase-separated complex coacervate domains bridged by the uncharged, hydrophilic PEO midblock. The resulting structures were studied by small-angle X-ray scattering (SAXS) and dynamic mechanical spectroscopy. The organization of the coacervate domains was shown to affect substantially the viscoelastic properties of the hydrogels, with the storage modulus increasing significantly as the mixtures transformed from a disordered array of domains to an ordered BCC structure with increasing block copolymer concentration. As the polymer concentration was further increased to 30 wt %, a hexagonal structure appeared, which coincided with a 25% drop in the modulus. Further structural changes, resulting in variations in the viscoelastic response, were also induced through changes in salt concentration. The viscoelastic properties and the physical nature of the cross-links have important implications for the applicability of these gels as injectable drug delivery systems.