This Perspective summarizes the features and limitations of reversible addition–fragmentation chain transfer (RAFT) polymerization, highlighting its strengths and weaknesses, as our understanding of ...the process, from both a mechanistic and an application point of view, has matured over the past 20 years. It is aimed at both experts in the field and newcomers, including undergraduate and postgraduate students, as well as nonexperts in polymerization who are interested in developing their own polymeric structures by exploiting the simple setup of a RAFT polymerization.
Barriers to therapeutic transport in biological systems can prevent accumulation of drugs at the intended site, thus limiting the therapeutic effect against various diseases. Advances in synthetic ...chemistry techniques have recently increased the accessibility of complex polymer architectures for drug delivery systems, including branched polymer architectures. This article first outlines drug delivery concepts, and then defines and illustrates all forms of branched polymers including highly branched polymers, hyperbranched polymers, dendrimers, and branched–linear hybrid polymers. Many new types of branched and dendritic polymers continue to be reported; however, there is often confusion about how to accurately describe these complex polymer architectures, particularly in the interdisciplinary field of nanomedicine where not all researchers have in‐depth polymer chemistry backgrounds. In this context, the present review describes and compares different branched polymer architectures and their application in therapeutic delivery in a simple and easy‐to‐understand way, with the aim of appealing to a multidisciplinary audience.
Recent examples of branched polymers are highlighted, including highly branched polymers, hyperbranched polymers, dendrimers, and branched–linear hybrid polymers, and their use as drug delivery systems. Aspects of synthesis and biological application are discussed, and benefits of different polymer structures compared.
We describe an optimized method to prepare multiblock copolymers. The approach is based on our previously reported use of reversible addition–fragmentation chain transfer (RAFT) polymerization, which ...here has been optimized into a fast, versatile, efficient, and scalable process. The one-pot, multistep sequential polymerization proceeds in water, to quantitative yields (>99%) for each monomer addition, thus circumventing requirements for intermediate purification, in 2 h of polymerization per block. The optimization of the process is initially demonstrated via the synthesis of a model decablock homopolymer (10 blocks) of 4-acryloylmorpholine with an average degree of polymerization of 10 for each block ( Đ = 1.15 and livingness >93% for the final polymer). Both the potential and the limitations of this approach are illustrated by the synthesis of more complex high-order multiblock copolymers: a dodecablock copolymer (12 blocks with 4 different acrylamide monomers) with an average degree of polymerization of 10 for each block and two higher molecular weight pentablock copolymers (5 blocks with 3 different acrylamide monomers) with an average degree of polymerization of 100 per block.
Artificial light-harvesting systems in aqueous media which mimic nature are of significant importance; however, they are often restrained by the solubility and the undesired aggregation-caused ...quenching effect of the hydrophobic chromophores. Here, we report a generalized strategy toward the construction of efficient artificial light-harvesting systems based on supramolecular peptide nanotubes in water. By molecularly aligning the hydrophobic chromophores along the nanotubes in a slipped manner, an artificial light-harvesting system with a two-step sequential Förster resonance energy transfer process is successfully fabricated, showing an energy transfer efficiency up to 95% and a remarkably high fluorescence quantum yield of 30%, along with high stability. Furthermore, the spectral emission could be continuously tuned from blue through green to orange, as well as outputted as a white light continuum with a fluorescence quantum yield of 29.9%. Our findings provide a versatile approach of designing efficient artificial light-harvesting systems and constructing highly emissive organic materials in aqueous media.
A new synthesis of hyperbranched polymers is outlined. This paper presents the synthesis of hyperbranched polymers by the recently highlighted thiol−yne reaction. In the thiol−yne reaction, a ...catalytic amount of photoinitiator and UV radiation are used to add two thiols across one alkyne bond at room temperature. This work demonstrates how the thiol−yne reaction can be used to form hyperbranched polymers from both small organic molecules and polymeric chains bearing an alkyne and a thiol. The UV-catalyzed reaction is fast, forming high-molecular-weight polymers after 20 min of UV irradiation. Hyperbranched polymers made by the thiol−yne reaction have the potential to serve as new materials for a variety of applications from catalytic support and drug delivery to viscosity modification.
The chemical structure and function of biomacromolecules has evolved to fill many essential roles in biological systems. More specifically, proteins, peptides, nucleic acids and polysaccharides serve ...as vital structural components, and mediate chemical transformations and energy/information storage processes required to sustain life. In many cases, the properties and applications of biological macromolecules can be further expanded by attaching synthetic macromolecules. The modification of biomacromolecules by attaching a polymer that changes its properties in response to environmental variations, thus affecting the properties of the biomacromolecule, has led to the emergence of a new family of polymeric biomaterials. Here, we summarize techniques for conjugating responsive polymers to biomacromolecules and highlight applications of these bioconjugates reported so far. In doing so, we aim to show how advances in synthetic tools could lead to rapid expansion in the variety and uses of responsive bioconjugates.
An examination on living or controlled and racial polymerization (CLRP) among dispersed systems is presented. Topics covered include the concept of nanoreactors, miniemulsion polymerization, ...morphological aspects and surface-initiated polymerization.
We report the synthesis by the reversible addition–fragmentation chain transfer process of well-defined decablock polymers with a final dispersity as low as 1.15 and a fraction of living chain as ...high as 97% after 10 successful block extensions, each taken to >99% monomer conversion. By using model decablock homopolymers of poly(N,N-dimethylacrylamide) and poly(4-acryloylmorpholine) of relatively low DP (10 units per block in average), we describe the theoretical and experimental considerations required to access high-order multiblock copolymers with excellent control over molecular weight distributions and high livingness.
Bioapplications of RAFT Polymerization Boyer, Cyrille; Bulmus, Volga; Davis, Thomas P ...
Chemical reviews,
11/2009, Volume:
109, Issue:
11
Journal Article
Peer reviewed
A discussion of possible biomedical applications of RAFT polymers is presented. RAFT polymerization has huge potential in the design of polymers for gene therapy, drug delivery, and many other uses.
Synthesis of (multi)block copolymers using reversible addition–fragmentation chain transfer (RAFT) polymerization generally suffers from the limitation that the order of the blocks must be ...considered. Herein, syntheses of block copolymers by RAFT polymerization using trithiocarbonate RAFT species are conducted as solution, miniemulsion, and emulsion polymerizations to demonstrate that the issue of monomer order for styrene and butyl methacrylate can be largely overcome in emulsion polymerization under carefully chosen conditions. The presence of monomer droplets in emulsion polymerizationin addition to polymer particles that constitute the locus of polymerizationleads to a reduction in the ratio of RAFT end groups to monomer at the locus of polymerization. Consequently, fragmentation of the RAFT adduct radical in the “backward” (“wrong”) direction is associated with fewer monomer additions, thus minimizing the impact of this undesired kinetic event. It is demonstrated that RAFT emulsion polymerization can be exploited to prepare an alternating pentablock copolymer composed of methacrylates (with 10 mol % styrene) and styrene without consideration of monomer order, thereby significantly broadening the scope of RAFT polymerization for multiblock copolymer synthesis.
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