Reducing the Degree of Branching in Polyacrylates via Midchain Radical Patching: A Quantitative Melt-State NMR Study

Advanced spectroscopy, microscopy, diffraction and thermal analysis of polyamide adhesives and prediction of their functional properties with solid-state NMR spectroscopy

Advanced spectroscopy, microscopy, diffraction and thermal analysis reveal heterogeneity and dynamics in polyamide industrial adhesives; solid-state NMR spectroscopy enable the prediction of their functional properties.

Effect of anethole on the copolymerization of vinyl monomers

Copolymerization behavior of Anethole with common vinyl monomers, determination of reactivity ratios via nonlinear least square method and the effect of Anethole on molecular weight and branching of copolymers produced via batch and semi-batch processes were reported.

Degree of branching in poly(acrylic acid) prepared by controlled and conventional radical polymerization

Poly(acrylic acid)s, PAAs and poly(sodium acrylate)s, PNaAs were characterized in detail.

Characterization of oligo(acrylic acid)s and their block co-oligomers

Oligo(acrylic acid), oligoAA are important species currently used industrially in the stabilization of paints and also for the production of self-assembled polymer structures which have been shown to have useful applications in analytical separation methods and potentially in drug delivery systems. To properly tailor the synthesis of oligoAA, and its block co-oligomers synthesized by Reversible-Addition Fragmentation chain Transfer (RAFT) polymerization to applications, detailed knowledge about the chemical structure is needed. Commonly used techniques such as Size Exclusion Chromatography (SEC) and Electrospray Ionization-Mass Spectrometry (ESI-MS) suffer from poor resolution and non-quantitative distributions, respectively. In this work free solution Capillary Electrophoresis (CE) has been thoroughly investigated as an alternative, allowing for the separation of oligoAA by molar mass and the RAFT agent end group. The method was then extended to block co-oligomers of acrylic acid and styrene. Peak capacities up to 426 were observed for these 1D CE separations, 10 times greater than what has been achieved for Liquid Chromatography (LC) of oligostyrenes. To provide a comprehensive insight into the chemical structure of these materials ¹H and ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy was used to provide an accurate average chain length and reveal the presence of branching. The chain length at which branching is detected was investigated with the results showing a degree of branching of 1% of the monomer units in oligoAA with an average chain length of 9 monomer units, which was the shortest chain length at which branching could be detected. This branching is suspected to be a result of both intermolecular and intramolecular transfer reactions. The combination of free solution CE and NMR spectroscopy is shown to provide a near complete elucidation of the chemical structure of oligoAA including the average chain length and branching as well as the chain length and RAFT agent end group distribution. Furthermore, the purity in terms of the dead chains and unreacted RAFT agent was quantified. The use of free solution CE and ¹H NMR spectroscopy demonstrated in this work can be routinely applied to oligoelectrolytes and their block co-oligomers to provide an accurate characterization which allows for better design of the materials produced from these oligomers.

Versatile Approach for the Synthesis of Sequence-Defined Monodisperse 18- and 20-mer Oligoacrylates

Linear monodisperse 18- and 20-mer acrylates are obtained via consecutive synthesis of two sequence-defined acrylate 9- and 10-mers, followed by disulfide coupling utilizing reversible addition-fragmentation chain transfer (RAFT) end group chemistry. The sequence-defined oligoacrylates are accessed via consecutive single (SUMI) and multiple (MUMI) unit monomer insertions through RAFT polymerization, using the extensive acrylate monomer library as functional building blocks. Aminolysis of the trithiocarbonate macroRAFT end group and in situ oxidation of the thiols to form a disulfide bridge lead to the formation of 18- and 20-mer acrylates. In this approach, one or multiple acrylate building blocks can be inserted in each step by chain extension to form a stable carbon-carbon backbone. Isolation of the targeted monodisperse oligomers, from the statistical mixtures obtained at first, is performed by flash column chromatography with high efficiency. It is shown that the SUMI and MUMI strategy, when combined with flash column chromatography separation, is highly efficient and allows to construct monodisperse materials of very considerable length starting from cheap and very versatile building blocks.

Analyzing the discrepancies in the activation energies of the backbiting and β-scission reactions in the radical polymerization of n-butyl acrylate

Activaton energies for backbiting and β-scission reactions for the polymerization of n-BA were determined by fitting experimental data to a mathematical model. The activation energy for backbiting was higher and that for β-scission lower than those accepted in the literature.

Functionalisation of MWCNTs with poly(lauryl acrylate) polymerised by Cu(0)-mediated and RAFT methods

We report the thermal and thermo-mechanical stability of poly(lauryl acrylate) P[LA] synthesised using RAFT and Cu(0)-mediated polymerisation methods and their interactions with multi-walled carbon nanotubes.

Determining the effect of side reactions on product distributions in RAFT polymerization by MALDI-TOF MS

RAFT polymerization has emerged as one of the most versatile reversible deactivation radical polymerization techniques and is capable of polymerizing a wide range of monomers under various conditions.

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.

Size-exclusion chromatography (SEC) of branched polymers and polysaccharides

Branched polymers are among the most important polymers, ranging from polyolefins to polysaccharides. Branching plays a key role in the chain dynamics. It is thus very important for application properties such as mechanical and adhesive properties and digestibility. It also plays a key role in viscous properties, and thus in the mechanism of the separation of these polymers in size-exclusion chromatography (SEC). Critically reviewing the literature, particularly on SEC of polyolefins, polyacrylates and starch, we discuss common pitfalls but also highlight some unexplored possibilities to characterize branched polymers. The presence of a few long-chain branches has been shown to lead to a poor separation in SEC, as evidenced by multiple-detection SEC or multidimensional liquid chromatography. The local dispersity can be large in that case, and the accuracy of molecular weight determination achieved by current methods is poor, although hydrodynamic volume distributions offer alternatives. In contrast, highly branched polymers do not suffer from this extensive incomplete separation in terms of molecular weight.

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