Sequence-regulated copolymers via tandem catalysis of living radical polymerization and in situ transesterification

Concurrent control over sequence and dispersity in multiblock copolymers

Controlling monomer sequence and dispersity in synthetic macromolecules is a major goal in polymer science as both parameters determine materials' properties and functions. However, synthetic approaches that can simultaneously control both sequence and dispersity remain experimentally unattainable. Here we report a simple, one pot and rapid synthesis of sequence-controlled multiblocks with on-demand control over dispersity while maintaining a high livingness, and good agreement between theoretical and experimental molecular weights and quantitative yields. Key to our approach is the regulation in the activity of the chain transfer agent during a controlled radical polymerization that enables the preparation of multiblocks with gradually ascending (Ɖ = 1.16 → 1.60), descending (Ɖ = 1.66 → 1.22), alternating low and high dispersity values (Ɖ = 1.17 → 1.61 → 1.24 → 1.70 → 1.26) or any combination thereof. We further demonstrate the potential of our methodology through the synthesis of highly ordered pentablock, octablock and decablock copolymers, which yield multiblocks with concurrent control over both sequence and dispersity.

A photo–thermal dual-regulated latent monomer strategy for sequence control of polymers

A photo–thermal dual-regulated latent monomer was used for the synthesis of polymers with advanced sequence structures.

One-pot synthesis for gradient copolymers via concurrent tandem living radical polymerization: mild and selective transesterification of methyl acrylate through Al(acac)3 with common alcohols

The acrylate based gradient copolymers were successfully synthesized by concurrent tandem living radical polymerization using Al(acac)₃ as cocatalyst with common alcohols.

Macromolecular Engineering by Applying Concurrent Reactions with ATRP

Modern polymeric material design often involves precise tailoring of molecular/supramolecular structures which is also called macromolecular engineering. The available tools for molecular structure tailoring are controlled/living polymerization methods, click chemistry, supramolecular polymerization, self-assembly, among others. When polymeric materials with complex molecular architectures are targeted, it usually takes several steps of reactions to obtain the aimed product. Concurrent polymerization methods, i.e., two or more reaction mechanisms, steps, or procedures take place simultaneously instead of sequentially, can significantly reduce the complexity of the reaction procedure or provide special molecular architectures that would be otherwise very difficult to synthesize. Atom transfer radical polymerization, ATRP, has been widely applied in concurrent polymerization reactions and resulted in improved efficiency in macromolecular engineering. This perspective summarizes reported studies employing concurrent polymerization methods with ATRP as one of the reaction components and highlights future research directions in this area.

Rapid and Scalable Access to Sequence-Controlled DHDM Multiblock Copolymers by FLP Polymerization

An immortal N-(diphenylphosphanyl)-1,3-diisopropyl-4,5-dimethyl-1,3-dihydro-2H-imidazol-2-imine/diisobutyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum (P(NIⁱ Pr)Ph₂ /(BHT)Alⁱ Bu₂ )-based frustrated Lewis pair (FLP) polymerization strategy is presented for rapid and scalable synthesis of the sequence-controlled multiblock copolymers at room temperature. Without addition of extra initiator or catalyst and complex synthetic procedure, this method enabled a tripentacontablock copolymer (n=53, k=4, dp_n =50) to be achieved with the highest reported block number (n=53) and molecular weight (M_n =310 kg mol^-1 ) within 30 min. More importantly, this FLP polymerization strategy provided access to the multiblock copolymers with tailored properties by precisely adjusting the monomer sequence and block numbers.

Sequence-Rearranged Cocrystalline Polymer Network with Shape Reconfigurability and Tunable Switching Temperature

Switching temperature (T_sw) is a key parameter governing the service condition of shape memory polymers (SMPs). However, tuning T_sw of SMPs often requires sophisticated synthesis or intricate processing. Herein, we report a simple yet effective strategy to prepare the SMPs with tunable T_sw and good reconfigurability by using the cocrystalline polyesters as the reversible phase. The cocrystallizable copolyesters with rearranged sequences were prepared by the transesterification of mixed polyester diols and then photo-cross-linked to achieve the SMP networks. Cocrystallization of copolymer blocks endows the SMP networks tunable melting point and relatively high crystallinity, affording the network good shape fixing and recovery ability at body temperature. Besides, the dynamic nature of transesterification, that enables the network to have good shape reconfigurability, allows for the easy processing of SMPs with complicated shapes. The reconfigurable SMPs capable of actuating at the body temperature show great potential for use as biomedical devices.

DNA-Programmed Chemical Synthesis of Polymers and Inorganic Nanomaterials

DNA nanotechnology, based on sequence-specific DNA recognition, could allow programmed self-assembly of sophisticated nanostructures with molecular precision. Extension of this technique to the preparation of broader types of nanomaterials would significantly improve nanofabrication technique to lower nanometer scale and even achieve single molecule operation. Using such exquisite DNA nanostructures as templates, chemical synthesis of polymer and inorganic nanomaterials could also be programmed with unprecedented accuracy and flexibility. This review summarizes recent advances in the synthesis and assembly of polymer and inorganic nanomaterials using DNA nanostructures as templates, and discusses the current challenges and future outlook of DNA templated nanotechnology.

Gradient copolymer micelles: an introduction to structures as well as structural transitions

Exhibiting variation of the composition along a chain, gradient copolymers bring new blood to the old story of polymeric micelles. The gradient chain structure results in some special features in micellar structures and leads to unique structural transitions, potentially leading to new properties and applications. Henceforth, gradient copolymer micellar structures and their transitions from the viewpoint of soft matter physics will be reviewed. Concepts such as a diffuse interface, shrinkage-stretching of micelles, and intrinsic temperature responsiveness are summarized from current research, which highlight new characteristic structures, relaxation modes and novel properties of micelles, respectively.

Sequence-Regulated Supracolloidal Copolymers via Copolymerization-Like Coassembly of Binary Mixtures of Patchy Nanoparticles

Synthetic copolymers of molecular systems serve as an inspiration for creation of one-dimensional copolymer-like superstructures via coassembly of anisometric nanoparticles. In contrast to the covalent and molecular copolymers, the details of formation mechanisms of copolymer-like superstructures, as well as the factors determining their length and the sequences of arranged nanoparticles, are still poorly understood. Herein, we propose a joint theoretical-computational framework to probe into the coassembly mechanism and kinetics of binary mixtures of patchy nanoparticles. By applying the coarse-grained molecular dynamics simulations, it is demonstrated that the coassembly of patchy nanoparticles markedly resembles many aspects of molecular step-growth copolymerization, and the sequences of nanoparticles inside the copolymer-like superstructures can be finely regulated by the relative activity and the initial ingredient of patchy nanoparticles as well as the coassembly strategy. A quantitatively copolymerization-like model is developed to account for the coassembly kinetics of patchy nanoparticles and the sequence distribution of arranged nanoparticles, all governed by the elaborate design of lower-level building units. The jointly theoretical and simulated studies offer mechanistic insights into the copolymerization-like kinetics and the sequence prediction for the coassembly of binary mixtures of patchy nanoparticles, paving the way toward the rational design of copolymer-like superstructures with various sequences and functionalities.

Synthesis of strictly alternating copolymers by living carbanionic copolymerization of diphenylethylene with 1,3-pentadiene isomers

The living carbanionic alternating copolymerizations of 1,3-pentadiene isomers with DPE are reported, and yield well-defined alternating and highly stereoregular amorphous copolymers with controllable M_n, low Đ_M and predominantly trans-1,4 units.

Sequence-defined multifunctional polyethers via liquid-phase synthesis with molecular sieving

Synthetic chemists have devoted tremendous effort towards the production of precision synthetic polymers with defined sequences and specific functions. However, the creation of a general technology that enables precise control over monomer sequence, with efficient isolation of the target polymers, is highly challenging. Here, we report a robust strategy for the production of sequence-defined synthetic polymers through a combination of liquid-phase synthesis and selective molecular sieving. The polymer is assembled in solution with real-time monitoring to ensure couplings proceed to completion, on a three-armed star-shaped macromolecule to maximize efficiency during the molecular sieving process. This approach is applied to the construction of sequence-defined polyethers, with side-arms at precisely defined locations that can undergo site-selective modification after polymerization. Using this versatile strategy, we have introduced structural and functional diversity into sequence-defined polyethers, unlocking their potential for real-life applications in nanotechnology, healthcare and information storage.

Acrylate-Selective Transesterification of Methacrylate/Acrylate Copolymers: Postfunctionalization with Common Acrylates and Alcohols

Acrylate-selective transesterification of methacrylate/acrylate copolymers with alcohols was developed for a site-selective postfunctionalization technique of polymers without using specific monomers. Importantly, a common methyl acrylate efficiently works as a selective modification unit via transesterification coupled with a titanium alkoxide catalyst. The acrylate-selective transesterification is achieved owing to less steric hindrance of the carbonyl groups that are attached to the main chain without an α-methyl group. Typically, the acrylate pendants of dodecyl methacrylate/methyl acrylate (MA) random copolymers were selectively transesterified with benzyl alcohol (BzOH). The conversion of the pendent esters into benzyl esters proportionally increased with MA contents. Additionally, various alcohols were applicable to this MA-selective transesterification system.

Advanced Materials by Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) has been successfully employed for the preparation of various advanced materials with controlled architecture. New catalysts with strongly enhanced activity permit more environmentally benign ATRP procedures using ppm levels of catalyst. Precise control over polymer composition, topology, and incorporation of site specific functionality enables synthesis of well-defined gradient, block, comb copolymers, polymers with (hyper)branched structures including stars, densely grafted molecular brushes or networks, as well as inorganic-organic hybrid materials and bioconjugates. Examples of specific applications of functional materials include thermoplastic elastomers, nanostructured carbons, surfactants, dispersants, functionalized surfaces, and biorelated materials.

Self-regulation in chemical and bio-engineering materials for intelligent systems

Herein, the authors review the self-regulation system secured by well-designed hybrid materials, composites, and complex system. As a broad concept, the self-regulated material/system has been defined in a wide research field and proven to be of great interest for use in a biomedical system, mechanical system, physical system, as the fact of something such as an organisation regulating itself without intervention from external perturbation. Here, they focus on the most recent discoveries of self-regulation phenomenon and progress in utilising the self-regulation design. This paper concludes by examining various practical applications of the remarkable materials and systems including manipulation of the oil/water interface, cell out-layer structure, radical activity, electron energy level, and mechanical structure of nanomaterials. From material science to bioengineering, self-regulation proves to be not only viable, but increasingly useful in many applications. As part of intelligent engineering, self-regulatory materials are expected to be more used as integrated intelligent components.

Facile synthesis of advanced gradient polymers with sequence control using furan-protected maleimide as a comonomer

Diverse advanced gradient polymers, including simultaneous, hierarchical, di-blocky, symmetrical, and tri-blocky gradient polymers, were facilely fabricated by applying furan protected maleimide as a co-monomer.

One-Pot Synthesis of ABCDE Multiblock Copolymers with Hydrophobic, Hydrophilic, and Semi-Fluorinated Segments

The scope and accessibility of sequence-controlled multiblock copolymers is demonstrated by direct "in situ" polymerization of hydrophobic, hydrophilic and fluorinated monomers. Key to the success of this strategy is the ability to synthesize ABCDE, EDCBA and EDCBABCDE sequences with high monomer conversions (>98 %) through iterative monomer additions, yielding excellent block purity and low overall molar mass dispersities (Ð<1.16). Small-angle X-ray scattering showed that certain sequences can form well-ordered mesostructures. This synthetic approach constitutes a simple and versatile platform for expanding the availability of tailored polymeric materials from readily available monomers.

Synthetic upcycling of polyacrylates through organocatalyzed post-polymerization modification

The direct transformation of commercially available commodity polyacrylates into value-added materials was achieved. We demonstrate how 1,5,7-triazabicyclo[4.4.0]dec-5-ene, serving as a nucleophilic catalyst, can be used to catalyze acyl substitution reactions of acrylic polymers in the presence of alcohol and amine nucleophiles. Furthermore, we found that organocatalytic transesterification exhibits high selectivity towards sterically unhindered esters, thus providing a new route towards site-selective acyl substitution of macromolecular materials. Combining this methodology with reversible-deactivation radical polymerization (RDRP) techniques such as reversible addition-fragmentation chain-transfer (RAFT) polymerization allowed for the precise functionalization of sterically-differentiated acrylic copolymers and polymeric chain ends. We envision this approach to expedite functional polymer synthesis and provide access to functional macromolecules prepared from inexpensive, hydrolytically-stable polymeric precursors.

Sequence-controlled supramolecular terpolymerization directed by specific molecular recognitions

Nature precisely manipulates primary monomer sequences in biopolymers. In synthetic polymer sequences, this precision has been limited because of the lack of polymerization techniques for conventional polymer synthesis. Engineering the primary monomer sequence of a polymer main chain represents a considerable challenge in polymer science. Here, we report the development of sequence-controlled supramolecular terpolymerization via a self-sorting behavior among three sets of monomers possessing mismatched host-guest pairs. Complementary biscalix[5]arene-C60, bisporphyrin-trinitrofluorenone (TNF), and Hamilton's bis(acetamidopyridinyl)isophthalamide-barbiturate hydrogen-bonding host-guest complexes are separately incorporated into heteroditopic monomers that then generate an ABC sequence-controlled supramolecular terpolymer. The polymeric nature of the supramolecular terpolymer is confirmed in both solution and solid states. Our synthetic methodology may pave an avenue for constructing polymers with tailored sequences that are associated with advanced functions.Nature can precisely control monomer sequences in biopolymers, but this is somewhat problematic in the formation of synthetic polymers. Here the authors show sequence-controlled supramolecular terpolymerization via self-sorting behavior among three sets of monomers possessing mismatched host-guest pairs.

Direct Access to Functional (Meth)acrylate Copolymers through Transesterification with Lithium Alkoxides

A straightforward and efficient synthetic method that transforms poly(methyl methacrylate) (PMMA) into value-added materials is presented. Specifically, PMMA is modified by transesterification to produce a variety of functional copolymers from a single starting material. Key to the reaction is the use of lithium alkoxides, prepared by treatment of primary alcohols with LDA, to displace the methyl esters. Under optimized conditions, up to 65% functionalization was achieved and copolymers containing alkyl, alkene, alkyne, benzyl, and (poly)ether side groups could be prepared. The versatility of this protocol was further demonstrated through the functionalization of both PMMA homo and block copolymers obtained through either radical polymerization (traditional and controlled) or anionic procedures. The scope of this strategy was illustrated by extension to a range of architectures and polymer backbones.

Design of Multifunctional Nanogate in Response to Multiple External Stimuli Using Amphiphilic Diblock Copolymer

Nature uses the interplay between hydrophobic and electrostatic interactions of disordered proteins to orchestrate complicated molecular gates such as the nuclear pore complex to control the transport of biological masses. Inspired by nature, we here theoretically show that well-defined gate shape, sensitive response to pH and salt concentration, and selectivity in cargo transport can be simultaneously achieved by grafting amphiphilic diblock copolymers made of sequence-controlled hydrophobic and ionizable monomers on the inner surface of solid-state nanopore. As a result, multiple functions such as ionic gating and molecular filtering can be implemented into one single copolymer nanogate. The gate structure and thermodynamics is a result of the self-assembly of the sequence-designed copolymer in the confined geometry that minimizes the free energy of the system. Our theory further predicts a phase transition and discontinuous charge regulation of the confined copolymer that allows logical gating in biosensors and nanofluidic devices. As an example of application, a nanolocker with the potential of molecular pumping has also been designed with the cooperation of two amphiphilic copolymer gates. Our results highlight the importance of polymer sequence in nanogating, and these insights can be used to guide the rational design of polymer-coated smart nanopores.

Smart Polymers with Special Wettability

Surface wettability plays a key role in addressing issues ranging from basic life activities to our daily life, and thus being able to control it is an attractive goal. Learning from nature, both of its structure and function, brings us much inspiration in designing smart polymers to tackle this major challenge. Life functions particularly depend on biomolecular recognition-induced interfacial properties from the aqueous phase onto either "soft" cell and tissue or "hard" inorganic bone and tooth surfaces. The driving force is noncovalent weak interactions rather than strong covalent combinations. An overview is provided of the weak interactions that perform vital actions in mediating biological processes, which serve as a basis for elaborating multi-component polymers with special wettabilities. The role of smart polymers from molecular recognitions to macroscopic properties are highlighted. The rationale is that highly selective weak interactions are capable of creating a dynamic synergetic communication in the building components of polymers. Biomolecules could selectively induce conformational transitions of polymer chains, and then drive a switching of physicochemical properties, e.g., roughness, stiffness and compositions, which are an integrated embodiment of macroscopic surface wettabilities.

Color change of alternating copolymers with phenyl vinylethylene carbonate and N-phenylmaleimide in a solution and in the solid-state, depending on their structure

The alternating PVEC and PMI copolymers with various composition ratios exhibited reversible color changes such as halochromism in solution and in the solid-state.

Synthesis of fluorinated gradient copolymers via in situ transesterification with fluoroalcohols in tandem living radical polymerization

Fluorinated gradient copolymers were synthesized by the tandem catalysis of ruthenium-catalyzed living radical polymerization and titanium alkoxide-mediated transesterification of methyl methacrylate (MMA) with fluoroalcohols.

RAFT-mediated, visible light-initiated single unit monomer insertion and its application in the synthesis of sequence-defined polymers

In this communication, we report a catalyst-free methodology for single unit monomer insertion (SUMI) into reversible addition–fragmentation chain transfer (RAFT) agents initiated by low intensity visible light.