Cononsolvency in the ‘drunken’ state: the thermoresponsiveness of a new acrylamide copolymer in water–alcohol mixtures

Macromol. Rapid Commun.

2018

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Herein, a reversible addition-fragmentation chain transfer (RAFT) polymerization is introduced for reactive monomers like N-acryloylpyrrolidine or N,N-dimethylacrylamide working without a conventional radical initiator. As a very straightforward proof of principle, the method takes advantage of the usually inconvenient radical-generating hydroperoxide contaminations in cyclic ethers like tetrahydrofuran or 1,4-dioxane, which are very common solvents in polymer sciences. The polymerizations are surprisingly well controlled and the polymers can be extended with a second block, indicating their high livingness. "Solvent-initiated" RAFT polymerizations hence prove to be a feasible access to tailored materials with minimal experimental effort and standard laboratory equipment, only requiring the following ingredients: hydroperoxide-contaminated solvent, monomer, and RAFT agent. In other respects, however, the potential coinitiating ability of the used solvent is to be considered when investigating the kinetics of RAFT polymerizations or aiming for the synthesis of high-livingness polymers, e.g., multiblock copolymers.

“… b) PAPy macro‐RAFT agent synthesized in THF was used (

{\overset{M}{true}}_{n, app}

= 4.1 kDa,

{\overset{M}{true}}_{n, th}

= 7.7 kDa, Đ = 1.28); mc : monomer conversion;

{\overset{M}{true}}_{n, th}

: theoretical number‐average molecular weight calculated by

{\overset{M}{true}}_{n, th} = \frac{[monomer]}{[RAFT]} \times M_{monomer} \times m c + M_{RAFT}

;

{\overset{M}{true}}_{n, app}

: apparent number‐average molecular weight determined by DMAc‐SEC with PMMA calibration; The discrepancy between

{\overset{M}{true}}_{n, app}

and

{\overset{M}{true}}_{n, th}

Section: Resultsmentioning

confidence: 99%

Hydroperoxide Traces in Common Cyclic Ethers as Initiators for Controlled RAFT Polymerizations

Eggers

Macromol. Rapid Commun.

2018

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“…Besides control of molecular weight and molecular weight distributions also the microstructure (e.g., tacticity or other types of isomerisms) can be controlled in many polymers. Homopolymers, random copolymers, block copolymers can be synthesized in very controlled ways by various means of polymerization techniques like controlled radical and ionic polymerizations, but also by metallocene‐catalyzed polymerizations . Also hybrid block copolymers can be prepared in controlled ways by combining biopolymers with synthetic polymers .…”

Section: Introductionmentioning

confidence: 99%

Functional Macromolecular Systems: Kinetic Pathways to Obtain Tailored Structures

Macro Chemistry & Physics

Kremer

Müller

et al. 2018

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This article aims to stimulate research on non‐equilibrium macromolecular systems, as nowadays a large toolbox to synthesize tailored macromolecules is available. A large variety of characterization methods covering a broad spectrum of length and timescales allows researchers to follow and also manipulate macromolecular systems on their paths toward equilibrium. These possibilities are paralleled by the development of new concepts of the statistical physics of non‐equilibrium phenomena in macromolecular systems as well as new models and algorithms for computer simulation.

“…Furthermore, the large variety and complexity of still regularly unpredictable stimuli‐related behavior makes fundamental research on the underlying mechanisms very important to date. Just to name a few, ongoing debates are held on cononsolvency phenomena, salting‐in and salting‐out effects, stimuli‐triggered aggregation mechanisms, and on the origins of upper and lower critical solution temperature‐type (UCST‐ and LCST‐type, respectively) behavior . Further remarkable research goes into the direction of time‐programmed stimuli‐responsive self‐assembly and superfast actuation …”

Section: Introductionmentioning

confidence: 99%

“…For instance, UCST‐ b ‐LCST‐type thermoresponsive block copolymers can show so‐called schizophrenic self‐assembly in water, meaning that their micellar core–shell structure can be inverted under proper conditions . Statistical copolymers of different thermoresponsive building blocks furthermore offer the advantage that their PTT is gradually adjustable in a range between the PTTs of the pure thermoresponsive polymeric components . Also, the incorporation of hydrophobic or hydrophilic comonomers can lower or increase the PTT, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Highly different water solubilities of the comonomers are additionally beneficial, since this widens the range of accessible PTTs of the created aqueous copolymer systems. To meet those requirements, our group recently investigated a new statistical copolymer system containing poly( N ‐acryloylpiperidine) (PAPi, LCST = 4 °C) and poly( N ‐acryloylpyrrolidine) (PAPy, LCST = 47 °C) . Further reports on PAPi or PAPy are actually rare in literature, nevertheless a few interesting publications exist.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Double thermoresponsive block–random copolymers with adjustable phase transition temperatures: From block‐like to gradient‐like behavior

Eggers

Eckert

J. Polym. Sci. Part A: Polym. Chem.

2017

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Stimuli‐responsive block–random copolymers are very useful “smart” materials as their switching behavior can be tuned by simply adjusting the composition of the random copolymer block. Because of that, we synthesized double thermoresponsive poly(N‐acryloylpyrrolidine)‐block‐poly(N‐acryloylpiperidine‐co‐N‐acryloylpyrrolidine) (PAPy‐b‐P(APi‐co‐APy)) copolymers via reversible addition fragmentation chain transfer (RAFT) polymerization and investigated their temperature‐induced self‐assembly in aqueous solution. By varying the APi/APy ratio in the random copolymer block, its phase transition temperature (PTT1) can indeed be precisely adjusted while the temperature‐induced collapse upon heating leads to a fully reversible well‐defined micellization. By making the two blocks compositionally similar to more than 60%, the polymers' mechanistic thermoresponsiveness can furthermore be changed from block‐like to rather gradient‐like behavior. This means the micellization onset at PTT1 and the corona collapse at the PTT of the more hydrophilic pure PAPy block (PTT2) overlap resulting in one single broad transition. This work thus contributes to the detailed understanding of design, synthesis and mechanistic behavior of tailored “on‐demand” switchable materials. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 399–411