Industrially-relevant polymerization-induced self-assembly formulations in non-polar solvents: RAFT dispersion polymerization of benzyl methacrylate

Industrially-sourced mineral oil and a poly(α-olefin) are used as solvents for the reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization of benzyl methacrylate (BzMA) using a poly(lauryl methacrylate) macromolecular chain transfer agent (PLMA macro-CTA) at 90 °C. The insolubility of the growing PBzMA chains under such conditions leads to polymerization-induced self-assembly (PISA), whereby poly(lauryl methacrylate)-poly(benzyl methacrylate) (PLMA-PBzMA) diblock copolymer spheres, worms or vesicles are produced directly as concentrated dispersions. The particular diblock copolymer composition required to access each individual morphology depends on the nature of the oil. Moreover, the solvent type also affects important properties of the physical free-standing gels that are formed by the PLMA-PBzMA worm dispersions, including the storage modulus (G′), critical gelation temperature (CGT) and critical gelation concentration (CGC). Spherical PLMA-PBzMA diblock copolymer nanoparticles can be prepared at up to 50% w/w solids and an efficient ‘one-pot’ protocol involving solution polymerization of LMA followed immediately by dispersion polymerization of BzMA has been developed. The latter formulation enables high BzMA conversions to be achieved, with spherical nanoparticles being produced at 30% w/w solids

Polymerization-induced self-assembly of block copolymer nanoparticles via RAFT non-aqueous dispersion polymerization

There is considerable current interest in polymerization-induced self-assembly (PISA) via reversible addition–fragmentation chain transfer (RAFT) polymerization as a versatile and efficient route to various types of block copolymer nano-objects. Many successful PISA syntheses have been conducted in water using either RAFT aqueous dispersion polymerization or RAFT aqueous emulsion polymerization. In contrast, this review article is focused on the growing number of RAFT PISA formulations developed for non-aqueous media. A wide range of monomers have been utilized for both the stabilizer and core-forming blocks to produce diblock copolymer nanoparticles in either polar or non-polar media (including supercritical CO2 and ionic liquids) via RAFT dispersion polymerization. Such nanoparticles possess spherical, worm-like or vesicular morphologies, often with controllable size and functionality. Detailed characterization of such sterically stabilized diblock copolymer dispersions provides important insights into the various morphological transformations that can occur both during the PISA synthesis and also on subsequent exposure to a suitable external stimulus (e.g. temperature)

Online coupling of two-dimensional liquid chromatography and NMR for the analysis of complex polymers

NatuurwetenskappeChemie & PolimeerwetenskapPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]

Two dimensional chromatographic characterization of block copolymers of 2-ethylhexyl acrylate and methyl acrylate, P2EHA-b-PMA, produced via RAFT-mediated polymerization in organic dispersion

For the precise characterization of block copolymers of 2-ethylhexyl acrylate (2EHA) and methyl acrylate (MA) produced via RAFT (reversible addition-fragmentation chain transfer)-mediated dispersion polymerization, novel liquid chromatographic separations have been developed. SEC showed multimodal molar mass distributions (MMD) and HPLC showed multimodal chemical composition distributions (CCD). The analyses of MMD and CCD of the reaction products indicated the formation of the expected block copolymer along with remaining P2EHA and PMA homopolymer fractions. Online coupling of SEC and gradient HPLC in a two-dimensional liquid chromatography (2D-LC) setup proved to be an efficient method to fractionate all polymer species present in the samples. Different kinds of copolymer molecules were identified in addition to the two homopolymers. The quantification of P2EHA using liquid chromatography at critical conditions (LC-CC) showed that the unreacted macro(RAFT agent) amount remained unchanged during at least the first 4 h of polymerization. LC-CC experiments also allowed the relative molar mass of the PMA blocks contained in the copolymers to be determined. The implementation of 2D-LC combining SEC and LC-CC allowed a more precise characterization of the different copolymer structures in particular in terms of block size. Finally, the results obtained by SEC/HPLC were confirmed by LC-1H NMR (proton nuclear magnetic resonance) experiments. It was concluded that the dispersed state of the polymerization system was the important factor for the formation of broadly distributed, complex copolymers when using a dithiobenzoate-based reactive macromolecular stabilizer. The detailed characterization of the system highlighted the enhancement of irreversible termination at the interface of the dispersed particles. © 2010 American Chemical Society.Articl

Association between childhood dimensions of attention deficit hyperactivity disorder and adulthood clinical severity of bipolar disorders

International audienceBackground: Clinical features of attention deficit hyperactivity disorder can be frequently observed in cases with bipolar disorders and associated with greater severity of bipolar disorders. Although designed as a screening tool for attention deficit hyperactivity disorder, the Wender Utah Rating Scale could, given its factorial structure, be useful in investigating the early history of impulsive, inattentive or mood-related symptoms among patients with bipolar disorders. Methods: We rated the Wender Utah Rating Scale in 276 adult bipolar disorder cases and 228 healthy controls and tested its factorial structure and any associations with bipolar disorder phenomenology. Results: We confirmed a three-factor structure for the Wender Utah Rating Scale (‘ impulsivity/temper’, ‘ inattentiveness’ and ‘ mood/self-esteem’). Cases and controls differed significantly on Wender Utah Rating Scale total score and sub-scale scores ( p-values < 10 −5 ). About 23% of bipolar disorder cases versus 5% of controls were classified as ‘ WURS positive’ (odds ratio = 5.21 [2.73–9.95]). In bipolar disorders, higher Wender Utah Rating Scale score was associated with earlier age at onset, severity of suicidal behaviors and polysubstance misuse; multivariate analyses, controlling for age and gender, confirmed the associations with age at onset ( p = 0.001) and alcohol and substance misuse ( p = 0.001). Conclusion: Adults with bipolar disorders who reported higher levels of childhood symptoms on the Wender Utah Rating Scale presented a more severe expression of bipolar disorders in terms of age at onset and comorbidity. The Wender Utah Rating Scale could be employed to screen for attention deficit hyperactivity disorder but also for ‘ at-risk behaviors’ in adult bipolar disorder cases and possibly for prodromal signs of early onset in high-risk subjects