Can percolation theory explain the gelation behavior of diblock copolymer worms?
Can percolation theory explain the gelation behavior of diblock copolymer worms?
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DOI：
10.1039/c8sc02406e
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发表时间：
2018-09-21
期刊：
影响因子：
8.4
通讯作者：
Armes SP
中科院分区：
文献类型：
--
作者：
Lovett JR;Derry MJ;Yang P;Hatton FL;Warren NJ;Fowler PW;Armes SP
嵌段共聚物蠕虫的物理凝胶作用可以用渗透理论解释为蠕虫之间的多次接触，这表明蠕虫纠缠在这种情况下是无关的。众所周知，聚合诱导自组装（PISA）为生产高各向异性双嵌段共聚物蠕虫提供了一条有效的合成途径。当在水培养基中制备时，这种蠕虫形成热反应性的独立水凝胶，这些水凝胶(i)易于灭菌，（ii）可以作为正常哺乳动物细胞培养的3D基质，（iii）可以诱导人类干细胞菌落停滞。在这里，我们严格检查两种类型的二嵌段共聚物蠕虫的凝胶行为，根据最新进展的渗透理论的刚性棒，这明确地说明了杆长多分散性的影响。更具体地说，我们使用小角度x射线散射（SAXS）来确定重量平均蜗杆轮廓长度Lw和平均蜗杆截面半径r。这种方法可以直接比较凝胶化所需的理论临界蜗杆体积分数φc与流变学测量和管倒置实验表明的实验值。考虑到这些双嵌段共聚物蠕虫相对灵活，而不是真正的棒状蠕虫，这两个参数之间的一致性相当好，特别是对于较短、相对坚硬的蠕虫。对于更长的、更灵活的蠕虫，需要一个大约为2的比例常数来调和φc的理论值和实验值。这些发现有望对其他各向异性纳米颗粒（如纤维素纳米晶和半晶嵌段共聚物棒）以及形成纤维的小分子（如二肽）凝胶的水凝胶行为产生重要影响。
Physical gelation by block copolymer worms can be explained in terms of multiple inter-worm contacts using percolation theory, suggesting that worm entanglements are irrelevant in this context. It is well known that polymerization-induced self-assembly (PISA) offers an efficient synthetic route for the production of highly anisotropic diblock copolymer worms. When prepared in aqueous media, such worms form thermoresponsive free-standing hydrogels that are (i) readily sterilizable, (ii) can act as a 3D matrix for the culture of normal mammalian cells and (iii) can induce stasis in human stem cell colonies. Herein we critically examine the gelation behavior of two types of diblock copolymer worms in terms of recent advances in percolation theory for rigid rods, which explicitly account for the effect of rod length polydispersity. More specifically, we use small-angle X-ray scattering (SAXS) to determine the weight-average worm contour length, Lw, and the mean worm cross-sectional radius, R. This approach enables a direct comparison to be made between the theoretical critical worm volume fraction, φc, required for gelation and the experimental values indicated by rheological measurements and tube inversion experiments. Given that these diblock copolymer worms are relatively flexible rather than truly rod-like, reasonably good agreement between these two parameters is observed, particularly for shorter, relatively stiff worms. For longer, more flexible worms a proportionality constant of approximately two is required to reconcile theory with experimental values for φc. These findings are expected to have important implications for the aqueous gelation behavior exhibited by various other anisotropic nanoparticles, such as cellulose nanocrystals and semicrystalline block copolymer rods, and also fibril-forming small molecule (e.g. dipeptide) gelators.
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影响因子：
18.2
作者：
Canton I;Warren NJ;Chahal A;Amps K;Wood A;Weightman R;Wang E;Moore H;Armes SP
通讯作者：
Armes SP
DOI：
10.1039/f29767201525
发表时间：
1976-01-01
期刊：
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS II
影响因子：
--
作者：
ISRAELACHVILI, JN;MITCHELL, DJ;NINHAM, BW
通讯作者：
NINHAM, BW
影响因子：
4.4
作者：
Banerjee, P;Mandal, BM
通讯作者：
Mandal, BM
影响因子：
5.5
作者：
Dalhaimer, P;Bates, FS;Discher, DE
通讯作者：
Discher, DE
影响因子：
15
作者：
Hirst, Andrew R.;Coates, Ian A.;Smith, David K.
通讯作者：
Smith, David K.