Preparation And Characterization Of Comb-like Multi-polyrotaxane By Free-radical Polymerization

Rotaxanes are consisting of macrocyclic compounds (as rotor) threaded on a polymerchain (as axis) by non-covalent bonds, where dissociation of the rings from the chain issignificantly sterically hindered by bulky moieties (so-called stoppers) usually attached to theends of the chain. The term pseudorotaxane describes rotaxanes without stoppers. It is calledmulti-polyrotaxane or multi-poly pseudorotaxane when more than one macrocycliccompounds are threaded on each chain. The cyclodextrins (CD)-based host-guest inclusioncomplexes are a series of important examples of multi-poly (pseudo) rotaxane. Side-chainpoly (pseudo-) rotaxanes with CD locating in polymer side chains have the features of variousstructures designing and varied preparation methods, can achieve a variety of functions incombination to build more complex supramolecular systems through designed polymer sidechains. Recent years, study on self-assembly supramolecular with new functions has becomeone of the hotspots of materials researches, and has been widely used in many aspects, such asdrug transport, bioactive materials etc..In this paper, comb-like polymer of APEG-1200was polymerized by free-radicalpolymerization, APEG-1200as monomer and AIBN. as initiator. Then cyclodextrin-basedcomb-like multi-polypseudorotaxanes (CD-PPR) hydrogels were obtained according todifferent the polymer/α-CD ratio which were characterized by FT-IR、XRD、SEM andrheology etc.. It was showed that: the hydrogel of “tube” crystallization with comb-like PPRstructure was prepared by forming inclusion complex with polymer with lower molecularweight and α-CD; With increasing of α-CD, the crosslinking density of the hydrogel increased,which had a significant impact on the performance of the hydrogel, such as the greatercross-linking density of the hydrogel, the higher sol-gel transition temperature, the largerswelling value, the greater thixotropy and yield stress.In addition, cyclodextrin-based comb-like multi-polyrotaxanes (CD-PR) were preparedby radical copolymerization used MMA and AS.AS was the inclusion complex of SEM-25and α-CD.The productions were characterized by FT-IR、XRD、SEM、1H-NMR and TEMetc.. It was showed that: an SEM-25in the AS including5.61α-CD, constituted a typical“tube” crystallization; CD-PR samples with different content of MMA had a typical “core-shell” structure, wherein the PMMA hydrophobic segments as the “nuclear”, the AShydrophilic segments as the “shell”; With the increasing content of MMA, the morphology ofCD-PR gradually changed from amorphous particles to regular shape, and the homogeneity ofparticles size also increased, but further increased the amount of MMA, the homogeneity ofparticles size declined.Finally, the self-assembly behavior of CD-PR was further studied. A wide range ofself-assembled morphology were prepared by controlling the external conditions withoutchanging the composition of the polymer. It was showed that water content had a significantimpact on the self-assembly process of CD-PR, with increasing of water content, thetransmittance declined, the system appeared spherical, mixture of spherical and rod, rod andvesicle morphology successively. The nature and composition of the solvent also affected theassembly of CD-PR, a variety of morphologies (spherical micelles, rod, sheet, etc.) observedin the system of THF/water and dioxane/water; While in DMF/water system could justform spherical micelles.