Universal xanthate-mediated controlled free radical polymerizations of the “less activated” vinyl monomers

Preparation and characterization of polydopamine and n-butyl methacrylate copolymer coatings on titanium-nickel alloy stents

Cardiovascular diseases pose a significant global health threat, and stents play a crucial role in managing these diseases. However, challenges exist with respect to the poor adhesion of stent coatings. Cardiac stents are often composed of titanium-nickel (TiNi) alloys as the metallic component and poly(n-butyl methacrylate) (PBMA) as the coating. The poor adhesion of PBMA to TiNi alloy surface may cause detachment and subsequent thrombosis post-implantation. This study utilizes Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization to synthesize a novel block copolymer, PBMA-b-PVP, composed of PBMA and poly(N-vinylpyrrolidone) (PVP). TiNi alloy surfaces are functionalized with polydopamine (PDA) to enhance polymer coating adhesion. PBMA-b-PVP exhibits a remarkable improvement in adhesion from class 5 to class 0 and high coating stability after a 15 days immersion in a phosphate buffer solution. The corrosion current density is reduced by 44% with the incorporation of PDA into PBMA-b-PVP coatings, suggesting high corrosion resistance. PDA-functionalized coatings promote cell viability without cytotoxicity, suggesting high biocompatibility. This study provides a robust strategy for preparing stent coatings with high adhesion, corrosion resistance, and biocompatibility.

α-Amido Trifluoromethyl Xanthates: A New Class of RAFT/MADIX Agents

Xanthates have long been described as poor RAFT/MADIX agents for styrene polymerization. Through the determination of chain transfer constants to xanthates, this work demonstrated beneficial capto-dative substituent effects for the leaving group of a new series of α-amido trifluoromethyl xanthates, with the best effect observed with trifluoroacetyl group. The previously observed Z-group activation with a O-trifluoroethyl group compared to the O-ethyl counterpart was quantitatively established with Cex = 2.7 (3-4 fold increase) using the SEC peak resolution method. This study further confirmed the advantageous incorporation of trifluoromethyl substituents to activate xanthates in radical chain transfer processes and contributed to identify the most reactive xanthate reported to date for RAFT/MADIX polymerization of styrene.

Stereospecific Living Cationic Polymerization of N-Vinylcarbazole through the Design of ZnCl2-Derived Counteranions

Highly stereospecific living polymerization of N-vinylcarbazole (NVC) successfully proceeded via a cationic mechanism as a result of the elaborate design of counteranions using an initiating system consisting of CF₃SO₃H, nBu₄NX (X = Cl, Br, I), and a Lewis acid catalyst. The use of ZnCl₂ and an appropriate amount of nBu₄NCl quantitatively generated highly isotactic polymers (mm = 94%) with narrow molecular weight distributions (M_w/M_n ∼ 1.3) and molecular weights proportional to monomer conversion. In this system, a ZnCl₄^2- species, which was formed as a counteranion of the propagating carbocation, most likely contributed to the stereoregulation of the polymers because the mm value drastically varied depending on the polymerization conditions, such as the Lewis acid catalyst and amount of added salt. Isotactic poly(N-vinylcarbazole) (PVK) showed different properties than atactic PVK based on fluorescence and differential scanning calorimetry (DSC) analysis.

Reversible Addition-Fragmentation Chain Transfer Polymerization of Acrylonitrile under Irradiation of Blue LED Light

Compared to unhealthy UV or γ-ray and high-energy-consumption thermal external stimuli, the promising light emitting diode (LED) external stimulus has some outstanding technological merits such as narrow wavelength distribution, low heat generation and energy consumption, and safety for human beings. In this work, a novel reversible addition-fragmentation transfer (RAFT) polymerization system for acrylonitrile (AN) was developed under the irradiation of blue LED light at room temperature, using 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene (4CzIPN) as a novel radical initiator and 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as the typical chain transfer agent. Well-defined polyacrylonitrile (PAN) with a controlled molecular weight and narrow molecular weight distribution was successfully synthesized. This strategy may provide another effective method for scientific researchers or the industrial community to synthesize a PAN-based precursor of carbon fibers.

Pure white-light and colour-tuning of Eu3+–Gd3+-containing metallopolymer

The first example of Eu³⁺–Gd³⁺-containing metallopolymer Poly(2-co-NVK-co-4) was constructed to exhibit tunable photoluminescence and even direct white-light emission.

Synthesis of functionalized poly(vinyl acetate) mediated by alkyne-terminated RAFT agents

Two new xanthates with alkyne functionalities were synthesized for the reversible addition fragmentation chain transfer (RAFT) polymerization of vinyl acetate (VAc).

MALDI of synthetic polymers with labile end-groups

Mass spectrometry is increasingly used in the field of synthetic polymers as a fast and accurate technique for end-group analysis. More particularly, matrix-assisted laser desorption/ionization (MALDI) has gained much popularity because it allows quite simple mass spectra to be obtained, displaying a single distribution for each polymeric species present in the sample, in contrast to electrospray ionization (ESI) which readily promotes multiple charging for most polymers. A soft ionization process, ensuring the integrity of the species upon transfer into gas phase ions, is however mandatory for polymer end-group analysis since information about the chain terminations mainly rely on the m/z values measured for polymer adducts. As compared to ESI, MALDI is sometimes suspected to be a quite "hard" ionization technique, leading to spontaneous dissociation of ionized species either in the source or during their flight time. This issue is of particular concern for polymers carrying so-called fragile end-groups arising from their mode of synthesis. In particular, controlled radical polymerization (CRP) processes, one of the most important advances in the field of polymer science during the last 20 years, allow the production of polymers with well-defined molecular distribution and low polydispersities, but they are all based on the low dissociation energy of the chemical bond between the last monomer and the terminating group. As a result, if macromolecules are activated while being ionized, this end-group is prone to fragmentation and ions measured in the mass spectra do no longer reflect the original chain composition. However, different results are reported in the literature about the ability of MALDI to generate intact ions from CRP synthetic polymers. This article reviews MALDI MS data reported for synthetic polymers produced by atom transfer radical polymerization (ATRP), reversible addition-fragmentation transfer polymerization (RAFT), and nitroxide-mediated polymerization (NMP), the three most studied CRP techniques. The general principle of each polymerization process, which defines the structure of the end-groups in both targeted macromolecules and species arising from eventual side-reactions, is first briefly presented. An overview of MALDI data reported for samples obtained upon polymerization of different monomers are then commented for each polymerization techniques with regards to the success of the ionization method to generate intact cationic adducts and its propensity to distinguish in-source fragments from polymerization side-products.

Manganese(iii) acetylacetonate initiated RAFT polymerizations: an alternative and versatile RAFT initiator

Manganese(iii) acetylacetonate (Mn(acac)₃) was demonstrated to be a versatile and superior RAFT initiator for different kinds of monomers, RAFT agents and noticeably, for a wide range of temperatures.

Novel Complex Polymers with Carbazole Functionality by Controlled Radical Polymerization

This review summarizes recent advances in the design and synthesis of novel complex polymers with carbazole moieties using controlled radical polymerization techniques. We focus on the polymeric architectures of block copolymers, star polymers, including star block copolymers and miktoarm star copolymers, comb-shaped copolymers, and hybrids. Controlled radical polymerization ofN-vinylcarbazole (NVC) and styrene and (meth)acrylate derivatives having carbazole moieties is well advanced, leading to the well-controlled synthesis of complex macromolecules. Characteristic optoelectronic properties, assembled structures, and three-dimensional architectures are briefly introduced.

Living Radical Polymerization by the RAFT Process – A Third Update

This paper provides a third update to the review of reversible deactivation radical polymerization (RDRP) achieved with thiocarbonylthio compounds (ZC(=S)SR) by a mechanism of reversible addition-fragmentation chain transfer (RAFT) that was published in June 2005 (Aust. J. Chem. 2005, 58, 379). The first update was published in November 2006 (Aust. J. Chem. 2006, 59, 669) and the second in December 2009 (Aust. J. Chem. 2009, 62, 1402). This review cites over 700 publications that appeared during the period mid 2009 to early 2012 covering various aspects of RAFT polymerization which include reagent synthesis and properties, kinetics and mechanism of polymerization, novel polymer syntheses, and a diverse range of applications. This period has witnessed further significant developments, particularly in the areas of novel RAFT agents, techniques for end-group transformation, the production of micro/nanoparticles and modified surfaces, and biopolymer conjugates both for therapeutic and diagnostic applications.