Synthesis And Rheology Of Single-chain Nanoparticles Based On Vinylbenzocyclobutene

Single-chain cross-linked nanoparticles(SCNP)are prepared by intramolecular cross-linking reactions,with small diameters and structures similar to disordered proteins,which have attracted widespread attention.There are many synthesis methods of SCNP,and the cycloaddition reaction of benzocyclobutene is a more mature one,which has a simple principle and high efficiency,which is suitable for the efficient synthesis of SCNP.SCNP is a typical three-dimensional shape polymer with rich and diverse dynamic behavior that can be studied by rheological experiments.In this project,4-vinylbenzocyclobutene(BCB)was copolymerized with styrene as linear precursors and intermolecularly crosslinked to prepare SCNP,so as to explore the relationship between SCNP structure and relaxation kinetic behavior.In this project,a SCNP with star polymer as a precursor was synthesized,and its bulk relaxation kinetic behavior was studied by rheological tests.In this project,a series of phenylethyldilene-vinylbenzocyclobutene linear random copolymer precursors were prepared by Atom transfer radical polymerization(ATRP),and SCNP was synthesized by continuous drop addition to obtain SCNP with different degrees of crosslinking by adjusting the BCB content of the random copolymer precursor.In this project,polymer fractionation is also used to purify the precursor chain in the synthesis process.The resulting products were characterized by nuclear magnetic resonance spectroscopy(NMR),gel permeation chromatography(GPC),dynamic light scattering(DLS),and differential calorimetry(DSC).According to the characterization results,we found that the tightness of SCNP crosslinking synthesized by linear precursors is mainly affected by the degree of crosslinking of their precursors,and the molecular weight of the precursor is also affected to a certain extent.In this project,a microsample rheometer was used to perform a small oscillatory shear(SAOS)test on SCNP samples,and the linear viscoelastic behavior of the obtained SAOS curves was analyzed.We found that the melt relaxation kinetic behavior of SCNP is greatly affected by its degree of crosslinking and particle size,and generally the larger the degree of crosslinking or the larger the particle size,the longer the relaxation time of SCNP,and even under extreme conditions,the sample will show a "no relaxation" state.Finally,in this project,a four-arm star-shaped polymer was obtained by grafting a linear random copolymer of styrene-vinylbenzocyclobutene with a tetrafunctional "nuclear" compound after end-modification and grafting.SCNP was synthesized based on a similar method to linear polymers for a series of characterizations.After SAOS testing,we found that it may be more tightly crosslinked than SCNP,which uses linear polymers as precursors.