Chiroptical Properties of Homopolymers and Block Copolymers Synthesized from the Enantiomeric Monomers N-Acryloyl-L-Alanine and N-Acryloyl-D-Alanine Using Aqueous RAFT Polymerization

2006 ◽  
Vol 59 (10) ◽  
pp. 749 ◽  
Author(s):  
Brad S. Lokitz ◽  
Jonathan E. Stempka ◽  
Adam W. York ◽  
Yuting Li ◽  
Hitesh K. Goel ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Raft Polymerization ◽  
Mirror Image ◽  
Cd Spectra ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Biomimetic Polymers ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Analogous Model

Chiral homo- and block copolymers based on the enantiomeric monomers N-acryloyl-l-alanine (ALAL) and N-acryloyl-d-alanine (ADAL) were prepared directly in water using controlled reversible addition–fragmentation chain transfer (RAFT) polymerization. The polymerization of the chiral monomers proceeded in a controlled fashion producing the respective homopolymers, block copolymers, and a statistical copolymer with targeted molecular weights and narrow molecular weight distributions. The chiroptical activity of these biomimetic polymers and their analogous model compounds was investigated using circular dichroism (CD). P(ALAL) and P(ADAL) were shown to be optically active exhibiting mirror image CD spectra. In addition, statistical and enantiomeric block copolymers prepared at 1:1 stochiometric ratios exhibited virtually no optical activity.

Mechanism of CPDB-Mediated RAFT Polymerization of Methyl Methacrylate: Influence of Pressure and RAFT Agent Concentration

2009 ◽  
Vol 62 (11) ◽  
pp. 1484 ◽  
Author(s):  
Michael Buback ◽  
Wibke Meiser ◽  
Philipp Vana
Keyword(s):  
Methyl Methacrylate ◽  
Raft Polymerization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
Rate Of Polymerization ◽  
Weight Distributions ◽  
Raft Agent ◽  
Successful Control ◽  
Mma Polymerization

Reversible addition–fragmentation chain transfer (RAFT) polymerizations of methyl methacrylate (MMA) in bulk at 60°C were performed at five pressures up to 200 MPa using 2-(2′-cyanopropyl)dithiobenzoate (CPDB) as RAFT agent at concentrations between 1.5 × 10–3 and 2.0 × 10–2 mol L–1. Applying high pressure during polymerization increases the rate of polymerization, but no effect on polydispersity was observed. Molecular weight distributions and average molecular weights of the final polymer indicated the successful control of MMA polymerization even at low CPDB concentrations. The slight retardation observed is adequately described by the dependence the termination rate coefficient, kt, on the chain-length.

scholarly journals Synthesis and Characterization of Well-Defined SolubleAlq3- andZnq2-Functionalized Polymers via RAFT Copolymerization

2010 ◽  
Vol 2010 ◽  
pp. 1-7
Author(s):  
Chengchao Wang ◽  
Wei Zhang ◽  
Nianchen Zhou ◽  
Yansheng Qiu ◽  
Zhengping Cheng ◽  
...  
Keyword(s):  
Chain Transfer ◽  
Chain Extension ◽  
Aluminium Isopropoxide ◽  
Soluble Polymers ◽  
First Order ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Reversible Addition ◽  
Weight Distributions

The reversible addition-fragmentation chain transfer (RAFT) copolymerizations of 2-((8-hydroxyquinolin-5-yl)methoxy)ethyl methacrylate (HQHEMA) with styrene (St) or methyl methacrylate (MMA) were successfully carried out in the presence of 2-cyanoprop-2-yl dithionaphthalenoate (CPDN). The polymerization behaviors showed the typical living natures by the first-order polymerization kinetics, the linear dependence of molecular weights of the polymers on the monomer conversions with the relatively narrow molecular weight distributions(Mw/Mn), and the successful chain extension experiments. The soluble polymers having tris(8-hydroxyquinoline)aluminum (Alq3) and bis(8-hydroxyquinoline) znic(II) (Znq2) side chains were obtained via complexation of the polymers with aluminium isopropoxide or zinc acetate in the presence of monomeric 8-hydroxyquinoline, which had strong fluorescent emission at 520 nm. The obtained polymers were characterized by GPC, NMR, UV-vis, and fluorescent spectra.

scholarly journals Towards a Polymer-Brush-Based Friction Modifier for Oil

2021 ◽  
Vol 69 (4) ◽  
Author(s):  
Tobias A. Gmür ◽  
Joydeb Mandal ◽  
Juliette Cayer-Barrioz ◽  
Nicholas D. Spencer
Keyword(s):  
Block Copolymers ◽  
Raft Polymerization ◽  
Film Formation ◽  
Polymer Brush ◽  
Friction Reduction ◽  
Friction Modifier ◽  
Molecular Weights ◽  
Sliding Surfaces ◽  
Reversible Addition ◽  
Anchoring Groups

AbstractTo meet the need for oil-compatible friction modifier additives that can significantly reduce energy consumption in the boundary-lubrication regime, a macromolecular design approach has been taken. The aim was to produce a lubricious polymer film on the sliding surfaces. A series of readily functionalizable block copolymers carrying an oleophilic poly(dodecyl methacrylate) block and a functionalizable poly(pentafluorophenyl methacrylate) block of various lengths was synthesized by means of reversible addition-fragmentation chain-transfer (RAFT) polymerization. The poly(pentafluorophenyl methacrylate) block was used to attach surface-active nitrocatechol anchoring groups to the polymer. The friction-reduction properties of these polymers were assessed with 0.5 wt% solutions in hexadecane by means of rolling-sliding macroscopic tribological tests. Block copolymers with roughly equal block lengths and moderate molecular weights were significantly more effective at friction reduction than all other architectures investigated. They also displayed lower friction coefficients than glycerol monooleate—a commercially used additive. The film-formation ability of these polymers was examined using a quartz-crystal microbalance with dissipation (QCM-D), by monitoring their adsorption onto an iron oxide-coated QCM crystal. The polymer with highest lubrication efficiency formed a thin film of ~ 17 nm thickness on the crystal, indicating the formation of a polymer brush. Interferometric rolling-sliding experiments with the same polymer showed a separating film thickness of ~ 20 nm, which is consistent with the QCM-D value, bearing in mind the compression of the adsorbed layers on the two sliding surfaces during tribological testing. Graphical Abstract

Reversible-deactivation radical polymerization of chloroprene and the synthesis of novel polychloroprene-based block copolymers by the RAFT approach

RSC Advances ◽  
2014 ◽  
Vol 4 (98) ◽  
pp. 55529-55538 ◽  
Author(s):  
Jia Hui ◽  
Zhijiao Dong ◽  
Yan Shi ◽  
Zhifeng Fu ◽  
Wantai Yang
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Radical Polymerization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Reversible Deactivation ◽  
Raft Agent ◽  
Reversible Deactivation Radical Polymerization

Novel, well-defined PCP-based block copolymers (PSt-b-PCP and PMMA-b-PCP) with controlled number averaged molecular weights and molecular weight distributions can be prepared, employing EPDTB and CPDB, respectively, as the initial RAFT agent.

Synthesis of N-vinylcarbazole–N-vinylpyrrolidone amphiphilic block copolymers by xanthate-mediated controlled radical polymerization

2010 ◽  
Vol 88 (3) ◽  
pp. 228-235 ◽  
Author(s):  
Chih-Feng Huang ◽  
Jeong Ae Yoon ◽  
Krzysztof Matyjaszewski
Keyword(s):  
Block Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Controlled Radical Polymerization ◽  
Amphiphilic Block Copolymers ◽  
Force Microscopy ◽  
Molecular Weights ◽  
Atomic Force ◽  
Reversible Addition ◽  
Mode Atomic Force Microscopy

Amphiphilic block copolymers poly(N-vinylcarbazole)-b-poly(N-vinylpyrrolidone) (PNVK-b-PNVP) were prepared by xanthate-mediated reversible addition-fragmentation chain transfer (RAFT) polymerization. Both the PNVK and PNVP macroinitiators and the resulting block copolymers had molecular weights close to theoretical values, predicted for efficient initiation, in the range of Mn = 30 000 to 90 000. The block copolymers dissolved in several organic solvents but, depending on their composition, in methanol formed either micelles or large aggregates, as confirmed by dynamic light scattering. The presence of globular aggregates was confirmed by tapping mode atomic force microscopy.

Visible-light induced controlled radical polymerization of methacrylates with Cu(dap)2Cl as a photoredox catalyst

2016 ◽  
Vol 7 (25) ◽  
pp. 4226-4236 ◽  
Author(s):  
Wenchao Ma ◽  
Dong Chen ◽  
Yuhong Ma ◽  
Li Wang ◽  
Changwen Zhao ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Block Copolymers ◽  
Visible Light ◽  
Radical Polymerization ◽  
Visible Light Irradiation ◽  
Controlled Radical Polymerization ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
System P ◽  
Weight Distributions

Under visible light irradiation, block copolymers of PPEGMA-b-PMMA with high molecular weights and narrow molecular weight distributions are obtained starting from a PPEGMA macroinitiator in the presence of the Cu(dap)2Cl/Me6TREN catalytic system.

scholarly journals Towards a Polymer-Brush-Based Friction Modifier for Oil

2021 ◽  
Author(s):  
Tobias A. Gmür ◽  
Joydeb Mandal ◽  
Juliette Cayer-Barrioz ◽  
Nicholas D. Spencer
Keyword(s):  
Iron Oxide ◽  
Block Copolymers ◽  
Raft Polymerization ◽  
Film Formation ◽  
Polymer Brush ◽  
Friction Reduction ◽  
Friction Modifier ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Anchoring Groups

Abstract In the search for new, oil-compatible friction-modifier additives that can significantly reduce energy consumption by reducing the friction in the boundary-lubrication regime, a macromolecular-design approach has been taken. This involved the synthesis of a series of readily functionalizable block copolymers carrying an oleophilic poly(lauryl methacrylate) block and a functionalizable poly(pentafluorophenyl methacrylate) block of various lengths by means of reversible addition-fragmentation chain-transfer (RAFT) polymerization. The poly(pentafluorophenyl methacrylate) block was used to attach surface-active nitro-catechol anchoring groups to the polymer. The friction-reduction properties of these polymers were assessed using 0.5 wt.% solutions in hexadecane using rolling-sliding macroscopic tribological tests. Block copolymers with roughly equal block lengths and moderate molecular weights were significantly more effective at friction reduction than all other architectures investigated. They also displayed lower friction coefficients than glycerol monooleate, a commercially used additive. The film formation ability of these polymers was examined using a quartz-crystal microbalance with dissipation (QCM-D), by monitoring their adsorption onto an iron-oxide coated QCM crystal. The polymer with highest lubrication efficiency formed a thin film of ∼17 nm thickness on the iron-oxide coated QCM crystal, consistent with the formation of a polymer brush. Interferometric rolling-sliding experiments with the same polymer showed a separating film thickness of ∼20 nm, which is consistent with the QCM-D value, bearing in mind the compression of the adsorbed layers on the two sliding surfaces during tribological testing.

scholarly journals Tailoring Polymer Dispersity by Controlled Radical Polymerization: A Versatile Approach

2020 ◽  
Author(s):  
Richard Whitfield ◽  
Kostas Parkatzidis ◽  
Nghia Truong ◽  
Tanja Junkers ◽  
Athina Anastasaki
Keyword(s):  
Molecular Weight ◽  
Kinetic Modelling ◽  
Raft Polymerization ◽  
Good Control ◽  
Chain Extension ◽  
Molecular Weight Distributions ◽  
Polymer Properties ◽  
Reversible Addition ◽  
Wide Range ◽  
Weight Distributions

<p>Dispersity (<i>Ɖ</i>) can significantly affect polymer properties and is a key parameter in materials design; however, current methods do not allow for the comprehensive control of dispersity. They are limited in monomer scope, may require the use of flow-based systems and/or additional reagents (<i>e.g.</i> termination agents or co-monomers), and are often accompanied by multimodal molecular weight distributions, low initiator efficiencies or poor end-group fidelity. Herein, we report a straightforward and versatile batch method based on reversible addition-fragmentation chain transfer (RAFT) polymerization which enables good control over <i>Ɖ</i> of a wide range of monomer classes, including acrylates, acrylamides, methacrylates and styrene. In addition, our methodology is compatible with more challenging monomers such as methacrylic acid, vinyl ketone and vinyl acetate. Control over <i>Ɖ</i> is achieved by mixing two RAFT agents with sufficiently different transfer activities in various ratios, affording polymers with monomodal molecular weight distributions over a broad dispersity range (<i>Ɖ</i> ~ 1.09-2.10). Our findings were further supported by simulations through the use of deterministic kinetic modelling which was fully in line with our experimental data, further confirming the power of our methodology. The robustness of the concept is further demonstrated by the preparation of well-defined block copolymers via chain extension of all polymers regardless of the initial <i>Ɖ</i>.</p>

scholarly journals Tailoring Polymer Dispersity by Controlled Radical Polymerization: A Versatile Approach

2020 ◽  
Author(s):  
Richard Whitfield ◽  
Kostas Parkatzidis ◽  
Nghia Truong ◽  
Tanja Junkers ◽  
Athina Anastasaki
Keyword(s):  
Molecular Weight ◽  
Kinetic Modelling ◽  
Raft Polymerization ◽  
Good Control ◽  
Chain Extension ◽  
Molecular Weight Distributions ◽  
Polymer Properties ◽  
Reversible Addition ◽  
Wide Range ◽  
Weight Distributions

<p>Dispersity (<i>Ɖ</i>) can significantly affect polymer properties and is a key parameter in materials design; however, current methods do not allow for the comprehensive control of dispersity. They are limited in monomer scope, may require the use of flow-based systems and/or additional reagents (<i>e.g.</i> termination agents or co-monomers), and are often accompanied by multimodal molecular weight distributions, low initiator efficiencies or poor end-group fidelity. Herein, we report a straightforward and versatile batch method based on reversible addition-fragmentation chain transfer (RAFT) polymerization which enables good control over <i>Ɖ</i> of a wide range of monomer classes, including acrylates, acrylamides, methacrylates and styrene. In addition, our methodology is compatible with more challenging monomers such as methacrylic acid, vinyl ketone and vinyl acetate. Control over <i>Ɖ</i> is achieved by mixing two RAFT agents with sufficiently different transfer activities in various ratios, affording polymers with monomodal molecular weight distributions over a broad dispersity range (<i>Ɖ</i> ~ 1.09-2.10). Our findings were further supported by simulations through the use of deterministic kinetic modelling which was fully in line with our experimental data, further confirming the power of our methodology. The robustness of the concept is further demonstrated by the preparation of well-defined block copolymers via chain extension of all polymers regardless of the initial <i>Ɖ</i>.</p>

The Use of Novel F-RAFT Agents in High Temperature and High Pressure Ethene Polymerization: Can Control be Achieved?

2007 ◽  
Vol 60 (10) ◽  
pp. 788 ◽  
Author(s):  
Markus Busch ◽  
Marion Roth ◽  
Martina H. Stenzel ◽  
Thomas P. Davis ◽  
Christopher Barner-Kowollik
Keyword(s):  
Molecular Weight ◽  
High Pressure ◽  
High Temperature ◽  
Degree Of Polymerization ◽  
Molecular Weight Distributions ◽  
High Pressure High Temperature ◽  
Reversible Addition ◽  
Weight Distributions ◽  
Raft Agent ◽  
Initial Results

Simulations are employed to establish the feasibility of achieving controlled/living ethene polymerizations. Such simulations indicate that reversible addition–fragmentation chain transfer (RAFT) agents carrying a fluorine Z group may be suitable to establish control in high-pressure high-temperature ethene polymerizations. Based on these simulations, specific fluorine (F-RAFT) agents have been designed and tested. The initial results are promising and indicate that it may indeed be possible to achieve molecular weight distributions with a polydispersity being significantly lower than that observed in the conventional free radical process. In our initial trials presented here (using the F-RAFT agent isopropylfluorodithioformate), a correlation between the degree of polymerization and conversion can indeed be observed. Both the lowered polydispersity and the linear correlation between molecular weight and conversion indicate that control may in principle be possible.

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