Electrostatic Manipulation Of Polymer Nanofilm Compartmentalization In Polymerization-Induced Self-Assembly

Multi-compartmentalization of block copolymers has attracted great attention in recent years and has a wide application prospect in biomedical fields.Most of this kind of multi-compartmentalization is prepared by self-assembly in dilute solutions.The chain entanglement of polymer usually makes the phase separation insufficient and difficult to form a well-structured multi-compartment system.Polymerization-induced self-assembly can be used for the rapid in situ synthesis of block copolymer nanomaterials with different morphologies in high concentration solution,it has obvious advantages of mass production and wide application prospects.In this thesis,we use visible light-initiated polymerization-induced self-assembly which was established earlier by our group.By means of charge repulsion of polyionic blocks in water and ion-clustering in hydrophobic environment,we achieved the in situ manipulation of two dimensional self-assembly of ABC triblock terpolymers and successfully prepared monolayer supracolloidal nanofilms and multi-compartment monolayer nanofilms.Hence,we establish the manipulation mechanism of pH,polymer concentration and block copolymerization sequences and create a new PISA-based approach for the synthesis of multi-compartment nanofilms.Firstly,two macromolecular chain transfer agents(macro-CTAs)with narrow molecular weight distributions and roughly equal degree of polymerization are prepared,namely PHPMA39-b-PHisMA41-TTC(CTA-1)(TTC stands for trithiocarbonate end-group)and PHisMA43-b-PHPMA38-TTC(CTA-2).The two macro-CTAs have pH-responsive properties.At pH 2.5,macro-CTAs dissolve in water with a fully cationic block;the electrostatic repulsion leads to conventional aqueous photo-PISA.At pH 7.3,the cationic block transforms to a hydrophobic ionomer block with 10%cationic repeat units,and copolymer chains self-assemble into weakly cationic micelles.At pH 2.5,macro-CTAs dissolve in water with a fully cationic block;electrostatic repulsion leads to conventional aqueous photo-PISA,which is different from as-reported PISA systems in which micelles formed upon strong electrostatic repulsion.In this thesis,a single core-forming block was used to prepare monolayer colloidal nanofilms,indicating that electrostatic repulsion induced nanofilm compartmentalization.Nanofilm roughness and thickness increase with PDAAM chain length.The size of spherical building blocks also increases.Moreover,high solid content can descrease the electrostatic repulsion,and hence more compact colloidal nanofilms are obtained.The colloidal nanofilms prepared by CTA-1 are denser than those prepared by CTA-2 due to weakened electrostatic repulsion.At pH 7.3,cationic block transforms to a hydrophobic ionomer block with 10%cationic repeat units,and the copolymer chains self-assemble into weakly cationic micelles,which leads to seeded photo-PISA via self-assembly into discrete nanoclusters in the hydrophobic lamellar framework to form multicompartment monolayer nanofilms.Increasing PDAAM block length leads to significant clustered and thickened nanofilms.Compared with CTA-2 system,colloidal clustering occurs at lower DP value of the core-forming block in CTA-1 system,indicating that increase in core-forming block DP and block copolymer sequence can enhance colloidal clustering.In conclusion,this thesis succeeded in the preparation of monolayer colloidal films and multicompartment monolayer films through manipulating the elelctrostatic interactions of a charged blocks including electrostatic repulsion in aqueous media and ion-clustering in hydrophobic micro-environment,via adjusting solution pH,copolymer concentration,and block copolymer sequence in aqueous solution.The thickness,compactness,roughness and porosity of monolayer colloidal films can be effectively regulated.This electrostatic manipulation sheds new light on the rational design and preparation of multicompartment block copolymer two-dimensional nano-objects.