Department of Chemical and Biological Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
Department of Materials Science and Engineering , Northwestern University , Evanston , Illinois 60208 , United States.
ACS Nano. 2019 Aug 27;13(8):9298-9305. doi: 10.1021/acsnano.9b03900. Epub 2019 Aug 15.
We demonstrate that a highly charged polyelectrolyte confined in a spherical cavity undergoes reversible transformations between amorphous conformations and a four-fold symmetry morphology as a function of dielectric mismatch between the media inside and outside the cavity. Surface polarization due to dielectric mismatch exhibits an extra "confinement" effect, which is most pronounced within a certain range of the cavity radius and the electrostatic strength between the monomers and counterions and multivalent counterions. For cavities with a charged surface, surface polarization leads to an increased amount of counterions adsorbed in the outer side, further compressing the confined polyelectrolyte into a four-fold symmetry morphology. The equilibrium conformation of the chain is dependent upon several key factors including the relative permittivities of the media inside and outside the cavity, multivalent counterion concentration, cavity radius relative to the chain length, and interface charge density. Our findings offer insights into the effects of dielectric mismatch in packaging and delivery of polyelectrolytes across media with different relative permittivities. Moreover, the reversible transformation of the polyelectrolyte conformations in response to environmental permittivity allows for potential applications in biosensing and medical monitoring.
我们证明，在球形腔体内，当腔体内外介质的介电失配时，带有高电荷的聚电解质可以在无定形构象和四元对称形态之间发生可逆转变。由于介电失配引起的表面极化表现出额外的“约束”效应，这种效应在腔半径和单体与抗衡离子以及多价抗衡离子之间的静电强度的一定范围内最为明显。对于带电荷的腔，表面极化导致更多的抗衡离子吸附在外侧，进一步将受限聚电解质压缩成四元对称形态。链的平衡构象取决于几个关键因素，包括腔体内外介质的相对介电常数、多价抗衡离子浓度、腔半径与链长的比值以及界面电荷密度。我们的发现为研究聚电解质在不同相对介电常数的介质之间的封装和输送中介电失配的影响提供了深入了解。此外，聚电解质构象对环境介电常数的可逆转变允许在生物传感和医学监测中应用。
