Fabrication And Properties Of Functionalized Polystyrene Microporous Colloids And Electrospinning Fiber Membranes

Porous organic polymers(POPs)are functional materials with large specific surface area,low skeletal density and stable physical and chemical property,which have extensive applications in gas storage,separation,chemical catalysis,drug delivery and any other potential field and possess great scientific significance and industrial value.Up to now,a wide range of synthetic methods are adopted to produce diversified POPs,including typical covalent organic frameworks(COFs),metal-organic frameworks(MOFs),and so on.Among the above materials,HCPs have attracted significant attention due to the mild reaction conditions,flexible structure to design and inexpensive building blocks/monomers,which reinforce their easy scale-up.In a typic HCPs design,small precursor molecules with polymerizable double-bond,e.g.styrene,divinylbenzene or chloroprene,are fabricated through a classic polymerization technology and then an hypercrosslinking strategy,such as post-crosslinking or external crosslinking.At the same time,the as-prepared HCPs always exist as a powder,limiting its industrial application.Using commercial macromolecular polystyrene instead of traditional micromolecules as main unit could effectively reduce the preparation cost.To gain large-sized materials,electrostatic spinning technology was adopted to combine with hypercrosslinking technology.The above measures are conducive to improve the possibility of industrial application of HCPs.Herein,we use PS,instead of using monomers or expensive copolymers,the main building block to synthesize amino-functionalized hypercrosslinked polymer nanoparticles(AHCPNPs)via a two-step synthetic strategy.Firstly,hypercrosslinked polymer nanoparticles(HCPNPs)are synthesized via one-step hypercrosslinking strategy in a mixed solution of PS and poly(tert-butyl acrylate)-b-poly(styrene)(Pt BA-b-PS)copolymer;then AHCPNPs is fabricated by an ammonolysis reaction of HCPNPs.The AHCPNPs is expected to have an obvious core-shell structure and possess abundant surface-functionalized groups.At the same time,the formation mechanism of nanoparticles has been studied based on research data and then supports the following exploration experiment.To control the size and performance of AHCPNPs,different kinds of diblock copolymer and the different mass ratio of diblock copolymer to PS has been chosen for research.Compared with traditional HCPs,it also has the potential to display a high specific surface area,extremely high CO₂ capture ability and excellent recycle performance.To gain the large-sized membrane,we fabricate a flexible,large-sized nanoporous membrane composing of crosslinked polyvinyl alcohol/nanoparticles(CPVANPs)by an elelctrostatic spinning method based on amino-functionalized hypercrosslinked polymer nanoparticles(AHCPNPs).As shown in Scheme 1,a PVA/NPs fiber is first obtained by electrospinning of PVA and high content of AHCPNPs,which is mainly made from comercial polymer polystyrene(PS).Hierarchical nanoporous CPVANPs membrane could be achieved after post-crosslinking of PVA skeleton by diisocyanate.The types and mass content of nanoparticles are considered to significantly affect the properties of the membrane and it has also been studied accordingly.The membrane mainly composed of AHCPNPs(highest amount is up to 80 w%),is successfully fabricated,rather than containing only a small amount for filling.The membrane with large size up to decimete scale possess impressively high mechanical properties(136.78 MPa)and tensile properties,hierarchical porous structure from microporous to macroporous size with relatively high specific surface area(258.31 m² g^-1)and excellent CO₂capture capability(35.44 w%,8.07 mmol g^-1).The results also show that the membrane can be been used in oil-water separation with a high oil absorption capacity(55.88 g g^-1 for castor oil)and efficient separate ratio of the emulsified oil(1 m L castor oil in 10 m L water,18000 r/min,3 mins).Since the mebrane is mainly made from PS and PVA,the fabrication approach could open up a new avenue for low-cost design of industrial large-sized,flexible and hierarchical nanoporous membranes for gas and oil-water separation.