Preparation Of Polymer Nanomaterials With Complex Morphology Based On Polymerization Induced Self-assembly

Polymer nanomaterials are characterized by novel structure,diverse morphology,excellent performance and good biocompatibility.Therefore,they play an important role in many fields such as drug controlled release,biological imaging,bionic simulation and nano-catalysis.As a new and efficient method to prepare polymer nanomaterials,polymerization induced selfassembly has been widely concerned by researchers in the past ten years.Compared with the preparation concentration as low as 1 mg/m L in traditional solution assembly,the polymerization induced self-assembly method creatively increased the preparation concentration to 500 mg/m L.At the same time,the problem of heterogeneous polymerization for the preparation of polymorphic aggregates is solved.Since the polymerization induced selfassembly method was reported,a variety of self-assembly structures including spherical,linear,wormlike,vesicular and composite vesicles have been successfully prepared.However,as far as the research on polymerization induced self-assembly method is concerned,the research on the regulation mechanism of polymer assembly morphology is not thorough enough,the morphological evolution law is not clear,and there is a lack of exploration on the application of polymerization induced self-assembly method.It is found that the high molecular weight of block copolymers and the high asymmetry of hydrophilic and hydrophobic chain segments are the decisive factors for the preparation of polymer nanomaterials with complex morphology.In order to prepare multi-morphological polymer nanomaterials,the effects of polymerization time and feeding ratio on the assembly morphology were studied,the regulation and evolution of morphology were summarized,and the differences between conventional solution self-assembly and polymerization induced selfassembly of multi-morphological polymer nanomaterials under the same block copolymer structure were compared.Finally,functional macromolecular chain transfer agents were introduced to prepare polymer nanoparticles with stimulus-responsive and self-crosslinking properties in one step.In order to explore the factors influencing the polymerization induced self-assembly morphology,RAFT polymerization was used to prepare PAA macromolecular chain transfer agent with different degree of polymerization.The structure and molecular weight of PAA were characterized by NMR spectrometer and gel permeation chromatography respectively.Then,PAA-b-PS polymer nanomaterials were prepared by polymerization induced self-assembly in methanol with styrene as monomer,and the effects of polymerization time and PAA chain length on the assembly morphology were studied by dynamic light scattering and transmission electron microscope.It was found that the morphology of the aggregates changed from spherical-worm-vesicle-complex vesicle with the extension of polymerization time.At the same time,with the same monomer and chain transfer agent feeding ratio,the morphology of the assembly increased with the PAA chain length,and large complex structure complex vesicles-simple complex vesicles-monodisperse vesicles occur,indicating that the high molecular weight and high asymmetry of block polymers were the key factors for the preparation of complex morphology polymer nanomaterials.The P4VP-b-PS system was used to prove the applicability of the rule.Firstly,RAFT polymerization was used to prepare macromolecular chain transfer P4 VP,and its structure and molecular weight were characterized by NMR and GPC.Similarly,in the methanol with styrene as monomer through polymerization induced self-assembly method for the preparation of polymer nano materials were studied with transmission electron microscopy and monomer polymerization time and the feeding of chain transfer agent ratio on the morphology.With the increasing of polymerization time and the proportion of monomers,morphology of the aggregates changed from spherical-vesicles-composite vesicles,indicating that the ultrahigh molecular weight and the high asymmetry of block polymers were the main factors which affecting the morphology.During the preparation of the P4VP-b-PS polymer nanomaterials through traditional solutions self-assembly,when PS segment degree of polymerization,respectively 341,663,1112 and 1834,spherical,vesicle,dumbbell vesicles and tubular structure were preparation respectively,and the preparation of tubular structure in the preparation of polymer nanomaterials field is of great significance.Subsequently,we continued to increase the degree of polymerization of PS chain segment to 2681 and 3469,and prepared loose tubular cage structure and compact tubular cage structure,respectively.When the degree of polymerization of PS chain segment increased to 4703,pincushion of tubules was prepared.Through comparative analysis,it was found that under the same block copolymer structure,solution self-assembly can be used to prepare assemblies with more complex morphologies.Finally,the application of polymerization induced self-assembly was explored.By introducing boroic acid groups and combining them with electron-rich compounds and odihydroxyl compounds,polymer nanomaterials that could detect hydroxyquinoline and alizarin red were prepared.Siloxane modified polymer nanomaterials were prepared by introducing macromolecular chain transfer agents containing siloxane groups,and showed excellent selfcrosslinking property,which is expected to play an important role in column chromatography filler materials.