scholarly journals RAFT Emulsion Polymerization of Styrene Using a Poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) mCTA: Synthesis and Thermosensitivity

Polymers ◽  
2021 ◽  
Vol 14 (1) ◽  
pp. 62
Author(s):  
Katharina Nieswandt ◽  
Prokopios Georgopanos ◽  
Martin Held ◽  
Evgeni Sperling ◽  
Volker Abetz
Keyword(s):  
Emulsion Polymerization ◽  
Diblock Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Molar Fraction ◽  
Solution Temperature ◽  
Hydrophobic Core ◽  
Spherical Micelle ◽  
Thermoresponsive Polymers ◽  
Isopropyl Acrylamide

Thermoresponsive poly((N,N-dimethyl acrylamide)-co-(N-isopropyl acrylamide)) (P(DMA-co-NIPAM)) copolymers were synthesized via reversible addition−fragmentation chain transfer (RAFT) polymerization. The monomer reactivity ratios were determined by the Kelen–Tüdős method to be rNIPAM = 0.83 and rDMA = 1.10. The thermoresponsive properties of these copo-lymers with varying molecular weights were characterized by visual turbidimetry and dynamic light scattering (DLS). The copolymers showed a lower critical solution temperature (LCST) in water with a dependence on the molar fraction of DMA in the copolymer. Chaotropic and kosmotropic salt anions of the Hofmeister series, known to affect the LCST of thermoresponsive polymers, were used as additives in the aqueous copolymer solutions and their influence on the LCST was demonstrated. Further on, in order to investigate the thermoresponsive behavior of P(DMA-co-NIPAM) in a confined state, P(DMA-co-NIPAM)-b-PS diblock copolymers were prepared via polymerization induced self-assembly (PISA) through surfactant-free RAFT mediated emulsion polymerization of styrene using P(DMA-co-NIPAM) as the macromolecular chain transfer agent (mCTA) of the polymerization. As confirmed by cryogenic transmission electron microscopy (cryoTEM), this approach yielded stabilized spherical micelles in aqueous dispersions where the PS block formed the hydrophobic core and the P(DMA-co-NIPAM) block formed the hydrophilic corona of the spherical micelle. The temperature-dependent behavior of the LCST-type diblock copolymers was further studied by examining the collapse of the P(DMA-co-NIPAM) minor block of the P(DMA-co-NIPAM)-b-PS diblock copolymers as a function of temperature in aqueous solution. The nanospheres were found to be thermosensitive by changing their hydrodynamic radii almost linearly as a function of temperature between 25 °C and 45 °C. The addition of kosmotropic salt anions, as a potentially useful tuning feature of micellar assemblies, was found to increase the hydrodynamic radius of the micelles and resulted in a faster collapse of the micelle corona upon heating.

scholarly journals Synthesis of Poly(3-vinylpyridine)-Block-Polystyrene Diblock Copolymers via Surfactant-Free RAFT Emulsion Polymerization

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3145 ◽  
Author(s):  
Katharina Nieswandt ◽  
Prokopios Georgopanos ◽  
Clarissa Abetz ◽  
Volkan Filiz ◽  
Volker Abetz
Keyword(s):  
Emulsion Polymerization ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Free Water ◽  
Monomer Conversion ◽  
Molecular Weights ◽  
Reversible Addition

In this work, we present a novel synthetic route to diblock copolymers based on styrene and 3-vinylpyridine monomers. Surfactant-free water-based reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene in the presence of the macroRAFT agent poly(3-vinylpyridine) (P3VP) is used to synthesize diblock copolymers with molecular weights of around 60 kDa. The proposed mechanism for the poly(3-vinylpyridine)-block-poly(styrene) (P3VP-b-PS) synthesis is the polymerization-induced self-assembly (PISA) which involves the in situ formation of well-defined micellar nanoscale objects consisting of a PS core and a stabilizing P3VP macroRAFT agent corona. The presented approach shows a well-controlled RAFT polymerization, allowing for the synthesis of diblock copolymers with high monomer conversion. The obtained diblock copolymers display microphase-separated structures according to their composition.

scholarly journals Doubly Dynamic Hydrogel Formed by Combining Boronate Ester and Acylhydrazone Bonds

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 487
Author(s):  
Yusheng Liu ◽  
Yigang Liu ◽  
Qiuxia Wang ◽  
Yugui Han ◽  
Hao Chen ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Diblock Copolymers ◽  
Raft Polymerization ◽  
Solid Content ◽  
Self Healing ◽  
Covalent Bonds ◽  
Boronate Ester ◽  
Isopropyl Acrylamide ◽  
Reversible Addition ◽  
The Difference

The incorporation of double dynamic bonds into hydrogels provides an effective strategy to engineer their performance on demand. Herein, novel hydrogels were PREPARED by combining two kinetically distinct dynamic covalent bonds, boronate ester and acylhydrazone bonds, and the synergistic properties of the hydrogels were studied comprehensively. The functional diblock copolymers P(N-isopropyl acrylamide-co-N-acryloyl-3-aminophenylboronic acid)-b-(N-isopropyl acrylamide-co-diacetone acrylamide) (PAD) were prepared via reversible addition−fragmentation chain transfer (RAFT) polymerization. The hydrogel was constructed by exploiting dynamic reaction of phenyboronic acid moieties with polyvinyl alcohol (PVA) and ketone moieties with adipic dihydrazide (ADH) without any catalyst. The active boronate ester linkage endows the hydrogel with fast gelation kinetics and self-healing ability, and the stable acylhydrazone linkage can enhance the mechanical property of the hydrogel. The difference in kinetics endows that the contribution of each linkage to mechanical strength of the hydrogel can be accurately estimated. Moreover, the mechanical property of the hydrogel can be readily engineered by changing the composition and solid content, as well as by controlling the formation or dissociation of the dynamic linkages. Thus, we provide a promising strategy to design and prepare multi-responsive hydrogels with tunable properties.

Star-Shaped Copolymers Based on Poly(N-vinylcaprolactam) and their Use as Nanocarriers of Methotrexate

2017 ◽  
Vol 70 (12) ◽  
pp. 1291 ◽  
Author(s):  
Norma A. Cortez-Lemus ◽  
Angel Licea-Claverie
Keyword(s):  
Polyethylene Glycol ◽  
Block Copolymers ◽  
Diblock Copolymers ◽  
Raft Polymerization ◽  
Drug Loading ◽  
Gel Permeation Chromatography ◽  
Solution Temperature ◽  
Star Copolymers ◽  
Vis Spectroscopy ◽  
Star Block Copolymers

Star-shaped poly(N-vinylcaprolactam)-block-poly(ethylhexylacrylate)-block-polyethylene glycol (PNVCL-b-PEHA-b-PEG) triblock copolymers and star-shaped poly(N-vinylcaprolactam)-block-polyethylene glycol (PNVCL-b-PEG) diblock copolymers were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. The resulting star block copolymers were characterized using 1H NMR and UV-vis spectroscopy, gel permeation chromatography, and dynamic light scattering. The star-shaped PNVCL-b-PEG and PNVCL-b-PEHA-b-PEG block copolymers self-assemble spontaneously into aggregates in water. The aggregates formed ranged from ~17 to 135 nm in diameter and were used to encapsulate methotrexate (MTX). It was observed that the aggregates from PNVCL-b-PEHA-b-PEG copolymers exhibited a higher drug loading and a lower release of MTX (19 wt-% and 54 %) as compared with star copolymers without PEHA (5 wt-% and 81 %) after 24 h at a temperature below their lower critical solution temperature values.

scholarly journals Thermoresponsive Polymers of Poly(2-(N-alkylacrylamide)ethyl acetate)s

Polymers ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 2464
Author(s):  
Xue Liu ◽  
Yuwen Hou ◽  
Yimin Zhang ◽  
Wangqing Zhang
Keyword(s):  
Ethyl Acetate ◽  
Raft Polymerization ◽  
Polymer Concentration ◽  
Degree Of Polymerization ◽  
Random Copolymers ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Induction Periods ◽  
Alkyl Groups ◽  
Cloud Point Temperature

Thermoresponsive poly(2-(N-alkylacrylamide) ethyl acetate)s with different N-alkyl groups, including poly(2-(N-methylacrylamide) ethyl acetate) (PNMAAEA), poly(2-(N-ethylacrylamide) ethyl acetate) (PNEAAEA), and poly(2-(N-propylacrylamide) ethyl acetate) (PNPAAEA), as well as poly(N-acetoxylethylacrylamide) (PNAEAA), were synthesized by solution RAFT polymerization. Unexpectedly, it was found that there are induction periods in the RAFT polymerization of these monomers, and the induction time correlates with the length of the N-alkyl groups in the monomers and follows the order of NAEAA < NMAAEA < NEAAEA < NPAAEA. The solubility of poly(2-(N-alkylacrylamide) ethyl acetate)s in water is also firmly dependent on the length of the N-alkyl groups. PNPAAEA including the largest N-propyl group is insoluble in water, whereas PNMAAEA and PNEAAEA are thermoresponsive in water and undergo the reversible soluble-to-insoluble transition at a critical solution temperature. The cloud point temperature (Tcp) of the thermoresponsive polymers is in the order of PNEAAEA < PNAEAA < PNMAAEA. The parameters affecting the Tcp of thermoresponsive polymers, e.g., degree of polymerization (DP), polymer concentration, salt, urea, and phenol, are investigated. Thermoresponsive PNMAAEA-b-PNEAAEA block copolymer and PNMAAEA-co-PNEAAEA random copolymers with different PNMAAEA and/or PNEAAEA fractions are synthesized, and their thermoresponse is checked.

scholarly journals Thermoresponsive and Redox Behaviors of Poly(N-isopropylacrylamide)-Based Block Copolymers Having TEMPO Groups as Their Side Chains

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Toru Uemukai ◽  
Tomoya Hioki ◽  
Manabu Ishifune
Keyword(s):  
Block Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Solution Temperature ◽  
Thermoresponsive Polymer ◽  
Critical Solution Temperature ◽  
Redox Active ◽  
Reversible Addition ◽  
Polymerization Conditions ◽  
Active Block

Thermoresponsive and redox-active block copolymers having 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) moieties have been synthesized by using the reversible addition-fragmentation chain transfer (RAFT) polymerization technique.N-Isopropylacrylamide (NIPAAm) and 2,2,6,6-tetramethylpiperidyl methacrylate (TEMPMA) monomers were copolymerized stepwise under RAFT polymerization conditions to afford the thermoresponsive block copolymers, PNIPAAm-block-PTEMPMA and PNIPAAm-block-PTEMPMA-block-PNIPAAm. Oxidation of tetramethylpiperidine groups in the copolymers successfully afforded the corresponding TEMPO-containing block copolymers. The resulting triblock copolymer was found to be thermoresponsive showing lower critical solution temperature (LCST) at 34∘C in its aqueous solution. Redox behavior of the resulting copolymer was observed by cyclic voltammetry. The potential of anodic current peak changed below and above the LCST of the block copolymer. These results indicate that the phase transition of thermoresponsive polymer influences the redox potential of TEMPO moieties.

scholarly journals Synthesis and Characterization of Temperature-Responsive N-Cyanomethylacrylamide-Containing Diblock Copolymer Assemblies in Water

Polymers ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 4424
Author(s):  
Nicolas Audureau ◽  
Fanny Coumes ◽  
Clémence Veith ◽  
Clément Guibert ◽  
Jean-Michel Guigner ◽  
...  
Keyword(s):  
Diblock Copolymer ◽  
Self Assembly ◽  
Diblock Copolymers ◽  
Colloidal Stability ◽  
Aqueous Dispersion ◽  
Degree Of Polymerization ◽  
Solution Temperature ◽  
Thermoresponsive Polymers ◽  
Aqueous Synthesis ◽  
Reversible Addition

We have previously demonstrated that poly(N-cyanomethylacrylamide) (PCMAm) exhibits a typical upper-critical solution temperature (UCST)-type transition, as long as the molar mass of the polymer is limited, which was made possible through the use of reversible addition-fragmentation chain transfer (RAFT) radical polymerization. In this research article, we use for the first time N-cyanomethylacrylamide (CMAm) in a typical aqueous dispersion polymerization conducted in the presence of poly(N,N-dimethylacrylamide) (PDMAm) macroRAFT agents. After assessing that well-defined PDMAm-b-PCMAm diblock copolymers were formed through this aqueous synthesis pathway, we characterized in depth the colloidal stability, morphology and temperature-responsiveness of the dispersions, notably using cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), small angle X-ray scattering (SAXS) and turbidimetry. The combined analyses revealed that stable nanometric spheres, worms and vesicles could be prepared when the PDMAm block was sufficiently long. Concerning the thermoresponsiveness, only diblocks with a PCMAm block of a low degree of polymerization (DPn,PCMAm < 100) exhibited a UCST-type dissolution upon heating at low concentration. In contrast, for higher DPn,PCMAm, the diblock copolymer nano-objects did not disassemble. At sufficiently high temperatures, they rather exhibited a temperature-induced secondary aggregation of primary particles. In summary, we demonstrated that various morphologies of nano-objects could be obtained via a typical polymerization-induced self-assembly (PISA) process using PCMAm as the hydrophobic block. We believe that the development of this aqueous synthesis pathway of novel PCMAm-based thermoresponsive polymers will pave the way towards various applications, notably as thermoresponsive coatings and in the biomedical field.

Hyperbranched Polymers via RAFT Copolymerization of an Acryloyl Trithiocarbonate

2007 ◽  
Vol 60 (6) ◽  
pp. 396 ◽  
Author(s):  
Andrew P. Vogt ◽  
Sudershan R. Gondi ◽  
Brent S. Sumerlin
Keyword(s):  
Click Chemistry ◽  
Lower Critical Solution Temperature ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Chain Transfer Agent ◽  
Solution Temperature ◽  
Dipolar Cycloaddition ◽  
Critical Solution Temperature ◽  
Reversible Addition ◽  
End Groups

Hyperbranched copolymers of N-isopropylacrylamide (NIPAM) and styrene were prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization in the presence of a novel acryloyl trithiocarbonate, namely 1-[3-(2-methyl-2-dodecylsulfanylthiocarbonylsulfanylpropionyloxy)propyl]-1H-[1,2,3]triazol-4-ylmethyl acrylate. By employing an example of ‘click chemistry’, we were able to prepare the vinyl RAFT chain transfer agent (CTA) by copper-catalyzed 1,3-dipolar cycloaddition of an azido-functionalized trithiocarbonate and propargyl acrylate. The resulting CTA facilitated the preparation of highly branched poly(N-isopropylacrylamide) (PNIPAM) and polystyrene. Interestingly, the branched PNIPAM demonstrated a reduced lower critical solution temperature (LCST) of 25°C as opposed to the conventional value of 32°C expected for linear PNIPAM, an effect attributed to increased contribution of hydrophobic dodecyl trithiocarbonate end groups.

Engineering of pH-triggered nanoplatforms based on novel poly(2-methyl-2-oxazoline)-b-poly[2-(diisopropylamino)ethyl methacrylate] diblock copolymers with tunable morphologies for biomedical applications

2021 ◽  
Author(s):  
Peter Černoch ◽  
Alessandro Jäger ◽  
Zulfia Cernochova ◽  
Vladimir Sincari ◽  
Lindomar Calumby Albuquerque ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Ring Opening ◽  
Biomedical Applications ◽  
Diblock Copolymers ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Amphiphilic Block Copolymers ◽  
Synthetic Approach ◽  
Ethyl Methacrylate ◽  
Reversible Addition

A two-step synthetic approach via the combination of living cationic ring-opening (CROP) and reversible addition-fragmentation chain transfer (RAFT) polymerization techniques was used to produce novel amphiphilic block copolymers based on...

Preparation and characterization of thermo-sensitive micelles composed of PSt-b-P(DEA-co-DMA)

e-Polymers ◽  
2008 ◽  
Vol 8 (1) ◽  
Author(s):  
Fengling Bian ◽  
Miao Xiang ◽  
Wei Yu ◽  
Mingzhu Liu
Keyword(s):  
Block Copolymer ◽  
Size Distribution ◽  
Chain Transfer ◽  
Polymeric Micelles ◽  
Raft Polymerization ◽  
Aqueous Media ◽  
Average Diameter ◽  
Distribution Patterns ◽  
Molar Ratio ◽  
Solution Temperature

AbstractThe amphiphilic block copolymer polystyrene-b-poly(N,Ndiethylacrylamide- co-N,N-dimethylacrylamide) (PSt-b-P(DEA-co-DMA)) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of DEA and DMA using PSt as macro chain transfer agent (PSt CTA) and N,N-azobisisobutyronitrile (AIBN) as initiator. Polymeric micelles were prepared by dialysis of the block copolymer solution in tetrahydrofuran (THF) against aqueous media. The polymeric micelles PM73 based on block copolymer P73, which was prepared with molar ratio DEA/DMA/PSt CTA/AIBN = 700:300:10:1, exhibited a lower critical solution temperature (39.2°C) in aqueous solution which was a little higher than the human body temperature. Polymeric micelles PM73 showed a unimodal size distribution with an average diameter of 24.2±0.5 nm. The micelles were thermodynamically stable in aqueous media above the critical micelle concentration (1 mg/l). The anti-inflammation drug, prednisone acetate, was incorporated into PM73 as the model drug. The loading capacity was found to be around 8 wt%, and the drug-loaded micelles showed similar size distribution patterns (monodisperse with an average diameter of 32.1±0.5 nm) and morphology (spherical) to the empty micelles. The drug-loaded micelles showed remarkable thermoresponsive drug release behavior, in response to the micellar structural change.

A new type of dual temperature sensitive triblock polymer (P(AM-co-AN)-b-PDMA-b-PNIPAM) and its self-assembly and gel behavior

2021 ◽  
Author(s):  
Cheng Zhou ◽  
Yan Chen ◽  
MingJun Huang ◽  
Yi Ling ◽  
Liming Yang ◽  
...  
Keyword(s):  
Self Assembly ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Temperature Sensitive ◽  
Temperature Responsive ◽  
Isopropyl Acrylamide ◽  
Reversible Addition ◽  
Triblock Polymer ◽  
New Type ◽  
Poly Acrylamide

A dual temperature-responsive triblock polymer (Poly(N-isopropyl acrylamide)-block-poly(N,N-dimethyl acrylamide)-block-poly(acrylamide-co-acrylonitrile) (P(AM-co-AN)-b-PDMA-b-PNIPAM) (NDAA) was obtained by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization ,with the uncharged UCST temperature-sensitive block P (AM-co-AN) and the...

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