scholarly journals Micellar Organocatalysis Using Smart Polymer Supports: Influence of Thermoresponsive Self-Assembly on Catalytic Activity

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2265
Author(s):  
Xiaoqian Yu ◽  
Artjom Herberg ◽  
Dirk Kuckling
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Smart Polymer ◽  
Polymer Supports ◽  
Ring Opening Reaction ◽  
Reversible Addition ◽  
Poly Ethylene ◽  
Shell Forming ◽  
Induced Aggregation

Micellar catalysts with a switchable core are attractive materials in organic synthesis. However, little is known about the role of the shell forming block on the performance of the catalyst. Thermoresponsive block copolymers based on poly(N-isopropylacrylamide-co-vinyl-4,4-dimethylazlactone) attached to different permanently hydrophilic blocks, namely poly(ethylene glycol), poly(N,N-dimethylacrylamide), and poly(2,3-dihydroxypropyl acrylate), were successfully synthesized via reversible addition/fragmentation chain transfer radical polymerization (RAFT). Post-polymerization attachment of an amino-functionalized L-prolineamide using the azlactone ring-opening reaction afforded functionalized thermoresponsive block copolymers. Temperature-induced aggregation of the functionalized block copolymers was studied using dynamic light scattering. It was shown that the chemical structure of the permanently hydrophilic block significantly affected the size of the polymer self-assemblies. The functionalized block copolymers were subjected to an aldol reaction between p-nitrobenzaldehyde and cyclohexanone in water. Upon temperature-induced aggregation, an increase in conversion was observed. The enantioselectivity of the polymer-bound organocatalyst improved with an increasing hydrophilic/hydrophobic interface as a result of the different stability of the polymer aggregates.

scholarly journals Role of Penetrability into a Brush-Coated Surface in Directed Self-Assembly of Block Copolymers

2018 ◽  
Vol 11 (3) ◽  
pp. 3571-3581 ◽  
Author(s):  
Laura Evangelio ◽  
Marta Fernández-Regúlez ◽  
Jordi Fraxedas ◽  
Marcus Müller ◽  
Francesc Pérez-Murano
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Coated Surface

scholarly journals Tuning Size and Morphology of mPEG-b-p(HPMA-Bz) Copolymer Self-Assemblies Using Microfluidics

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2572
Author(s):  
Jaleesa Bresseleers ◽  
Mahsa Bagheri ◽  
Coralie Lebleu ◽  
Sébastien Lecommandoux ◽  
Olivier Sandre ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Self Assembly ◽  
Size Difference ◽  
Flow Rates ◽  
Polymer Vesicles ◽  
Attractive Option ◽  
Self Assembled ◽  
Size And Morphology ◽  
Poly Ethylene ◽  
Careful Design

The careful design of nanoparticles, in terms of size and morphology, is of great importance to developing effective drug delivery systems. The ability to precisely tailor nanoparticles in size and morphology during polymer self-assembly was therefore investigated. Four poly(ethylene glycol)-b-poly(N-2-benzoyloxypropyl methacrylamide) mPEG-b-p(HPMA-Bz) block copolymers with a fixed hydrophilic block of mPEG 5 kDa and a varying molecular weight of the hydrophobic p(HPMA-Bz) block (A: 17.1, B: 10.0, C: 5.2 and D: 2.7 kDa) were self-assembled into nanoparticles by nanoprecipitation under well-defined flow conditions, using microfluidics, at different concentrations. The nanoparticles from polymer A, increased in size from 55 to 90 nm using lower polymer concentrations and slower flow rates and even polymer vesicles were formed along with micelles. Similarly, nanoparticles from polymer D increased in size from 35 to 70 nm at slower flow rates and also formed vesicles along with micelles, regardless of the used concentration. Differently, polymers B and C mainly self-assembled into micelles at the different applied flow rates with negligible size difference. In conclusion, this study demonstrates that the self-assembly of mPEG-b-p(HPMA-Bz) block copolymers can be easily tailored in size and morphology using microfluidics and is therefore an attractive option for further scaled-up production activities.

An isotopic effect in self-assembly of amphiphilic block copolymers: the role of hydrogen bonds

Soft Matter ◽  
2009 ◽  
Vol 5 (24) ◽  
pp. 5003 ◽  
Author(s):  
Rina Shvartzman-Cohen ◽  
Chun-lai Ren ◽  
Igal Szleifer ◽  
Rachel Yerushalmi-Rozen
Keyword(s):  
Block Copolymers ◽  
Hydrogen Bonds ◽  
Self Assembly ◽  
Isotopic Effect ◽  
Amphiphilic Block Copolymers

Synthesis of Polystyrene-B-Poly(Ethylene Oxide)monomethyl Ethermethacrylate Block Copolymers and its Self-Assembly in Aqueous Solution

2011 ◽  
Vol 284-286 ◽  
pp. 769-772
Author(s):  
Qian Qian You ◽  
Pu Yu Zhang
Keyword(s):  
Aqueous Solution ◽  
Molecular Weight ◽  
Block Copolymers ◽  
Self Assembly ◽  
Chain Transfer ◽  
Functional Group ◽  
Transmission Electron ◽  
Reversible Addition ◽  
Ft Ir ◽  
A Chain

The block copolymer of PSt-b-POEOMA with the end of -COOH functional group has been synthesized by reversible addition fragmentation chain-transfer (RAFT) using S,S′-Bis(α,α′-dimethyl-α′′-acetic acid)-trithiocarbonate (BDATC) as a chain transfer agent. The architectures of the copolymers were confirmed by FT-IR and 1HNMR spectra. GPC analysis was used to estimate the molecular weight and the molecular weight distribution of the copolymers. Meanwhile, The nanostructures of the block copolymers PSt-b-POEOMA micelles formed in aqueous solution were observed by transmission electron microscopy (TEM) and dynamic light scattering (DLS).

Room temperature aqueous self-assembly of poly(ethylene glycol)-poly(4-vinyl pyridine) block copolymers: From spherical to worm-like micelles

2016 ◽  
Vol 145 ◽  
pp. 447-453 ◽  
Author(s):  
Daniela P. Rodrigues ◽  
João R.C. Costa ◽  
Nuno Rocha ◽  
Joana R. Góis ◽  
Arménio C. Serra ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Ethylene Glycol ◽  
Self Assembly ◽  
Room Temperature ◽  
Poly Ethylene Glycol ◽  
Vinyl Pyridine ◽  
Poly Ethylene

Analysis of Thiol-sensitive Core-cross-linked Polymeric Micelles Carrying Nucleoside Pendant Groups using 'On-line' Methods: Effect of Hydrophobicity on Cross-linking and Degradation

2011 ◽  
Vol 64 (6) ◽  
pp. 766 ◽  
Author(s):  
Bianca M. Blunden ◽  
Donald S. Thomas ◽  
Martina H. Stenzel
Keyword(s):  
Block Copolymers ◽  
Polymeric Micelles ◽  
Raft Polymerization ◽  
Amphiphilic Block Copolymers ◽  
Cross Linking ◽  
Copolymer Composition ◽  
Reversible Addition ◽  
On Line ◽  
Styrene Content ◽  
Poly Ethylene

Amphiphilic block copolymers were prepared via reversible–addition fragmentation chain transfer (RAFT) polymerization and their synthesis, cross-linking, and degradation were studied using on-line monitoring. The focus of this work is the systematic alteration of the hydrophobic block using copolymers based on 5′-O-methacryloyluridine (MAU) and styrene at different compositions to determine the effect of the copolymer composition on the properties of the micelle. A poly(poly(ethylene glycol) methyl ether methacrylate) (PEGMA) macroRAFT agent was chain extended with a mixture of styrene and MAU. In both systems, an increasing fraction of styrene was found to reduce the rate of polymerization, but the functionality of the RAFT system was always maintained. The amphiphilic block copolymers were dialyzed against water to generate micelles with sizes between 17 and 25 nm according to dynamic light scattering (DLS). Increasing styrene content lead to smaller micelles (determined by DLS and transmission electron microscopy) and to lower critical micelle concentrations, which was measured using surface tensiometry. The micelles were further stabilized via core-cross-linking using bis(2-methacroyloxyethyl) disulfide as crosslinker. NMR analysis revealed a faster consumption of crosslinker with higher styrene content. These stable cross-linked micelles were investigated regarding their ability to degrade in the presence of dithiothreitol as a model reductant. Increasing the styrene content resulted in a faster degradation of the cross-linked micelles into unimers.

Sign in / Sign up

Export Citation Format

Share Document