Accelerated heterogenous ring-opening polymerization towards well-defined helical poly(N-allyl alanine)with clickable side chains

Well-defined poly(N-allyl alanine)has been synthesized by heterogenous ring-opening polymerization(HROP)of less reactive N-allyl-alanine N-carboxyanhydride,using acetic acid as the catalyst and benzylamine as the initiator,in non-polar n-hexane.Interestingly,the polymerization exhibited typical features of living polymerization though both monomer(liquid)and polymer(solid)have minimal solubility in n-hexane.The obtained polymer showed a stable helix structure independent of the temperatures screened,as evidenced by circular dichroism analysis.Also,the preliminary study demonstrated that the side chains can be post-functionalized through thiol-ene click chemistry with quantitative conversion.Together,this work provides guidance for the development of accelerated HROP of other liquid monomers bearing low reactivity.Besides,the helical and functionalizable poly(N-allyl alanine)could be a useful“clickable platform”for the design of variable biomaterials via efficient click chemistry.

Quantitative understanding of phase segregation behaviors by precisely building discrete oligo-ester-b-oligo-olefin block copolymers

Block copolymers(BCPs) with high Flory-Huggins parameter(χ) and balanced surface energy have aroused tremendous interest for ultra-small nanopatterns processing.However,high χ and balanced surface energy are generally contradicted.The fine tune of chain structure might be a useful way to achieve high χ and balanced surface energy.To realize this,the block copolymer with exactly uniform chain structure,i.e.,defined molecular structure,is highly desirable for accurately evaluating the phase behavior.Herein,two kinds of discrete oligo ester-b-oligo olefin block copolymers with different chemical structures(oligo lactic acid-boligo olefin BCP,oLA_(n)-b-C_(m);oligo phenyl lactic acid-b-oligo olefin BCP,oPL_(n)-b-C_(m)) were modularly synthesized through iterative growth methods.The effect of chain structure on segregation strength and surface properties was quantitatively investigated using the discrete BCPs as precise models.On the one hand,introducing rigid and nonpolar phenyl groups into oligo ester block has a negligible effect on the chemical incompatibility,as confirmed by the identical high χ values of oLA_(n)-b-C_(m) and oPL_(n)-b-C_(m)(χ_(oLA/C)=0.21 and χ_(oPL/C)=0.19).On the other hand,the incorporation of nonpolar phenyl groups creates balanced surface energy,that is,the high χ and balanced surface energy were simultaneously achieved by oPL_(n)-b-C_(m).Therefore,sub-10 nm perpendicular nanopatterns can be easily produced upon brief thermal treatment,demonstrating its potential application in semiconductor manufacturing with ultra-small feature size.The discrete BCP can serve as a quantitative and exquisite model to study the critical contribution of chain structures on phase separation behavior,providing insightful understanding to facilitate the potential application in the chip process.

Polymer Mechanochemistry on Reactive Species Generated from Mechanochemical Reactions

Comprehensive Summary Polymer mechanochemistry on reactive species has attracted more and more attentions over the past 20 years,as the mechanochemical generation of reactive species has a great potential in developing different polymeric materials for various purposes,such as stress detection,self-healing,self-strengthening,controllable degradation and release of small molecules.In this review,we first discuss the recent progress on polymer mechanochemistry of the reactive species that are generated from the mechanochemical reactions of mechanophores.Five types of reactive species,including radical,zwitterion,ionic,carbene and neutral intermediates,and their applications were reviewed in detail.Since mechanochemical reactions are sensitive to the mechanophore structure and polymer framework,we then discuss how mechanophore isomerism,polymer structure,polymer attachment point,and polymer architecture influence the mechanophore activation.At last,we provide our perspectives on the polymer mechanochemistry of reactivespecies.

Piezoelectrically Mediated Reactions:From Catalytic Reactions to Organic Transformations

Recently,piezocatalysis has attracted considerable attention as a new type of renewable mechanical energy conversion technology,which relies on the strain induced polarization of the piezoelectric material.This new technology has been extensively applied in the applications of water splitting,water remediation,gas purification and tumor therapy.Despite the rapid development in the piezo-catalysis,the utilization of piezoelectric materials for synthetic purpose is still under exploration.Piezoelectric means to promote or-ganic reactions expand the scope of piezoelectrically mediated reactions and show successes in both organic and polymer synthesis.Herein,we provide a comprehensive review on recent progress of piezoelectrically mediated reactions,catalytic mechanisms and applications in the last few years.The limitations and future directions of this area are also discussed.We believe this review will provide new insights into the underlying mechanism of piezoelectric mediated electron transfer process and guide the design of new chemistry.

Piezoelectric Zinc Oxides with High Polar Facets Ratios for Mechanically Controlled RAFT Polymerization

Mechanoredox chemistry that uses highly polarized piezoelectric materials as mechanoredox catalysts to promote redox reactions has emerged recently.It provides an alternative approach alongside the existing polymerization methods.Despite recent accomplishments,determining the quantitative relationship between the structure of ZnO and its catalytic performance for polymerization is still challenging.Herein,we prepared various ZnO crystals with different polar facets ratios to achieve efficient mechanically induced reversible addition-fragmentation chain transfer polymerization(mechano-RAFT).ZnO prepared from Zn(NO3)2 showed a high polar facet ratio of 1.66 and offered the highest catalytic activity among all ZnO samples.A near-quantitative initiator efficiency of 99.5%and narrow molecular weight distribution were achieved for the polymerization of n-butyl acrylate.Furthermore,the high chain-end fidelity and chain extension capability were also evidenced by MALDI-TOF MS and GPC analysis.This work highlighted the significant contribution of polar facets in ZnO to its catalytic activity and will guide the design of mechanoredox catalysis with superior catalytic performance in the future.

Bridging from the Sequence to Architecture: Graft Copolymers Engineering via Successive Latent Monomer and Grafting-from Strategies

The on-demand building copolymer structures,from sequence to architecture,is crucial in understanding the relation between pol-ymer structure and property,meanwhile motivating the innovation of polymer hierarchy.However,the challenge is conspicuous for,complicated polymer structures from inherently intricate polymerization.In this work,copolymers with tailored grafting density and distributions were achieved using successive latent monomer and grafting-from strategies.The hydroxyl group functionalized fu-ran/maleimide adduct(FMOH)was selected as the latent monomer for RAFT polymerization of an array of copolymers with tailored localization of hydroxyl group along the main chain.The hydroxyI group further initiated the ring opening polymerization(ROP)of L-lactide or ε-caprolactone,resulting in a library of multicomponent copolymers via grafting-from strategy.The initiating efficiency reached to-100% with variable molecular weight(21300-58600 Da)and narrow distributions(Ð_(M)<1.25),indicating that such graft copolymers possessed controlled density and distribution of side chains as its linear template.The investigation on thermal properties of the well-defined graft copolymers implied that the precise tailoring over copolymer structures at the molecule level could lead to tunable chemical/physical properties.This work bridged polymer from sequence to architecture,unveiled a new meth-od in creating graft copolymers with programmable structures and provided the insight into the structure/property relationship.

Maleimide Chemistry:Enabling the Precision Polymer Synthesis

Herein is presented a compilation of the main characteristics of maleimide chemistry in developing the precisely controlled polymers,including the design of sequence-controlled polymers,topological polymers,and polymeric single-chain nanoparticles.The synthetic methods,relied on the versatilities of the maleimide moieties as a latent monomer which leads to an efficient alternative in various innovative applications,especially in self-healing material,self-reporting materials for real-time monitoring,and also in data storage and anticounterfeiting technologies.The core of the content in this review is focused on the up-to-data advances and publications on the major of maleimide chemistry in our research group.

Recent advances in the synthesis of discrete oligomers and polymers: chemistry, strategy and technology

Nature creates a variety of biomacromolecules, such as DNA and proteins, with precisely defined chain lengths/molecular weights (MWs), monomer sequences, and topologies. In contrast, traditional synthetic polymers have an inhomogeneous composition, variation in chain length.