Haney Bobby, Werner Jörg G, Weitz David A, Ramakrishnan Subramanian
Department of Chemical and Biomedical Engineering, FAMU-FSU Engineering, Tallahassee, Florida 32310, United States.
Department of Mechanical Engineering and Division of Materials Science and Engineering, Boston University, Boston, Massachusetts 02215, United States.
ACS Appl Mater Interfaces. 2020 Jul 22;12(29):33439-33446. doi: 10.1021/acsami.0c11408. Epub 2020 Jul 13.
Microgel particles are cross-linked polymer networks that absorb certain liquids causing network expansion. The type of swelling fluid and extent of volume change depends on the polymer-liquid interaction and the network's cross-link density. These colloidal gels can be used to stabilize emulsion drops by adsorbing to the interface of two immiscible fluids. However, to enhance the adsorption abilities of these predominantly hydrophilic gel particles, some degree of hydrophobicity is needed. An amphiphilic Janus microgel with spatially distinct lipophilic and hydrophilic sides is desired. Here, we report the fabrication of poly(ethylene glycol) diacrylate/poly(propylene glycol) diacrylate Janus microgels (JM) using microfluidic drop making. The flow streams of the two separate and immiscible monomer solutions are brought into contact and intersected by a third immiscible fluid in a flow-focusing junction to form Janus droplets. The individual droplets are cross-linked via UV irradiation to form monodispersed microgel particles with opposing hydrophilic and hydrophobic 3D-networked polymer matrices. By combining two chemically different polymer gel networks, an amphiphilic emulsion stabilizer is formed that adsorbs to the oil-water interface while its faces absorb their respective water or hydrocarbon solvents. The resulting water-in-oil emulsions are stabilized and destabilized via a thermal-responsive hydrogel. Stimuli-responsive droplets are demonstrated by adding a short-chain oligo ethylene glycol acrylate molecule to the hydrogel formulation on the Janus microgel particle. Droplets stabilized by these particles experience a sudden increase in droplet diameter around 60 °C. This work with absorbent particles may prove useful for applications in bio catalysis, fuel production, and oil transportation.
微凝胶颗粒是交联聚合物网络，其吸收特定液体导致网络膨胀。溶胀流体的类型和体积变化程度取决于聚合物与液体的相互作用以及网络的交联密度。这些胶体凝胶可通过吸附到两种不混溶流体的界面来稳定乳液滴。然而，为了提高这些主要为亲水性凝胶颗粒的吸附能力，需要一定程度的疏水性。需要一种具有空间上不同的亲脂性和亲水性面的两亲性Janus微凝胶。在此，我们报告了使用微流控滴制法制备聚（乙二醇）二丙烯酸酯/聚（丙二醇）二丙烯酸酯Janus微凝胶（JM）。两种单独且不混溶的单体溶液的流股在流动聚焦结处与第三种不混溶流体接触并相交，形成Janus液滴。各个液滴通过紫外线照射交联，形成具有相对的亲水性和疏水性3D网络聚合物基质的单分散微凝胶颗粒。通过结合两种化学不同的聚合物凝胶网络，形成一种两亲性乳液稳定剂，其吸附到油水界面，而其表面吸收各自的水或烃类溶剂。所得的油包水乳液通过热响应水凝胶稳定和去稳定。通过在Janus微凝胶颗粒上的水凝胶配方中添加短链低聚乙二醇丙烯酸酯分子来证明刺激响应液滴。由这些颗粒稳定的液滴在60°C左右液滴直径会突然增加。这项关于吸收性颗粒的工作可能在生物催化、燃料生产和石油运输应用中证明是有用的。
