Self-assembly Of Amphiphilic Functional Block Copolymers And The Applications In Rubber-reinforced Nanometer Fillers

Self-assembly method is the spontaneous organization of components into ordered structures via non-covalent interactions,which has attracted much attention with the development of material science.Self-assembly has extended the traditional nano-scale chemistry to micro-or even macroscale,realizing a functional and stable material construction process.Block copolymer self-assembly,one of the important bottom-up methods in nanotechnology,has been widely used for the construction of functional materials.Reversible addition-fragmentation chain transfer(RAFT)polymerization is one of the effective methods to construct block copolymers.The benefits of RAFT polymerization are simple polymerization conditions,controllable molar mass,and broad application range of monomers.In this dissertation,a series of well-defined amphiphilic functional statistical,block and gradient copolymers were obtained by RAFT polymerization.In selective solvent,these amphiphilic copolymers could self-assemble into various aggregates with stimuliresponsive functions.The main research contents are as follows:1.A series of well-defined CO2-responsive gradient copolymers(PBzMA-b-P(DEAEMA-grad-NVP)-b-PNVP)were obtained through switchable RAFT polymerization.These amphiphilic gradient copolymers could self-assemble into various core-shell-corona multicompartment micelles in aqueous solution,and the assembled nanoaggregates widely presented the heterogeneous nanodomains surrounding the dark micelle cores.Upon treatment with CO2,the inhomogenous nature of gradient copolymers endowed nanoaggregates some unique stimuli-responsive behaviors,which came out with a patchy and heterogeneous shell structure.Furthermore,this gradient strategy may offer a novel way to design and realize precise morphological manipulation?2.In order to enlarge the benefits of amphiphilic gradient copolymers,a class of CO2-responsive statistical,block and gradient copolymers nanoobjects were prepared by batch or semi-batch RAFT polymerization.PEG macro-RAFT agents were used to control the polymerization of hydrophobic monomer BzMA and CO2-sensitive monomer DEAEMA.In the synthesis of well-defined gradient copolymers,semi-batch RAFT polymerization was performed by using a programmed syringe pump to achieve precise control over desired copolymer composition distribution.And in aqueous solution,these copolymers could self-assemble into various nanoaggregates.After treatment with CO2,the gradient copolymer aggregates transformed into nanosheet-like architectures,while the statistical and block copolymers with similar molecular weight could only form larger vesicles or disassemble.3.A class of RAFT-derived amphiphilic CO2/O2 dual gas-responsive triblock copolymers,PEG-b-P(DEAEMA-co-FMA)-b-PS were designed and synthesized.Based on the amphiphilic and gas-sensitive units,these triblock copolymers could self-assemble into typical nanotube structures,and after bubbling air into the aggregates solution,these nanotubes transformed into vesicle structures;at the same time,these vesicles could further undergo the volume expansion and contraction in alternating treatment with CO2 and O2,eventually rupture.The morphological transformations of these dual gas-responsive nano-objects successfully simulated the formation,respiration and apoptosis of alveoli,and provided an essential basis for exploring the life phenomena.4.RAFT dispersion polymerization of isoprene and styrene were conducted in ethanol by using PDMA as the macro-chain transfer agent.In this project,the rubber-based monomers isoprene and styrene are the main components.By polymerization induced self-assembly and in-situ crosslinking,the cross-linked nanometer assemblies with controllable morphology and good size homogeneity and dispersion could be prepared on a large scale and used as ideal filler for rubber reinforcement.It was found that the polymeric aggregates rubber reinforced fillers obviously improved the mechanical properties of the filled rubber materials.5.After the successful PISA process of isoprene and styrene in ethanol,we designed and prepared the polyisoprene-b-polystyrene nanoobjects via RAFT non-polar dispersion polymerization of styrene in hexane using polyisoprene as a macro-chain transfer agent.Under this condition,the polyisoprene macro-CTA was soluble in hexane,whereas the growing polystyrene became insoluble.Thus this RAFT non-polar dispersion polymerization led to the formation of well-defined spherical,worm-like and vesicular morphologies by changing the polymerization conditions,such as the DP of PIp and PS block,weight solid content,and reaction time.Uniquely,based on the special diblock copolymer composition and the good solubility of non-polar solvent hexane,the generated nano-objects could be used as rubber reinforced ideal fillers and significantly improved the mechanical properties of the filled rubber materials.