Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

• underlying structure–property relationships governing the thermoresponse of sterically constrained assemblies, are still poorly understood. Furthermore, the clear majority of publications deals with polymers that exhibit a lower critical solution temperature (LCST) behavior, with PNIPAAM as their main

• physicochemical interplay between the architecture of the polymer assembly and the resulting thermoresponsive switching behavior will be in the foreground of this consideration. Keywords: lower critical solution temperature (LCST); responsive coating; smart material; thermoresponsive polymer; upper critical

• of solvents. In solution, stimuli responsive polymers undergo a conformational, so-called coil-to-globule, transition. Depending on whether the solubility increases below (LCST for lower critical solution temperature [46][47][48][49]) or above (UCST for upper critical solution temperature [50][51][52

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• ). The results obtained were consistent with those reported by O’Reilly using a polymeric backbone with catalytic centres inside the chain [56]. The authors outlined the possibility of recycling the catalyst based on the lower critical solution temperature (LCST) of the catalytic polymer system. The

LCST phase behavior of benzo-21-crown-7 with different alkyl chains

• Yan Deng,
• Xing Li,
• Qiao Zhang,
• Zheng Luo,
• Chengyou Han and
• Shengyi Dong

Beilstein J. Org. Chem. 2019, 15, 437–444, doi:10.3762/bjoc.15.38

• -crown-7, B21C7s) can effectively control the thermo-responsive properties. Keywords: crown ethers; hydrophobic units; lower critical solution temperature; LCST; thermo-responsiveness; supramolecular chemistry; Introduction The introduction of stimuli-responsiveness into artificial materials is vital

• to design advanced functional materials [1][2][3][4][5][6][7]. An external thermal stimulus is often applied to supramolecular systems to realize reversible control over supramolecular self-assemblies [8][9][10][11][12][13]. In this context, lower critical solution temperature behavior, known as LCST

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• aggregation of the hydrophobic alkyl chain rings, which induced insolubilization of the bicyclic compound in aqueous media at 20 °C and a decrease in its clouding point. Keywords: amphiphilic molecules; host–guest complexes; lower critical solution temperature; pillar[n]arenes; pseudo[1]catenane

• ; Introduction Thermo-responsive molecules exhibiting a lower critical solution temperature (LCST) are very important for applications such as controlled drug release [1], molecular separation [2], and tissue culture substrates [3]. Poly(N-isopropylacrylamide) (pNIPAAm) is a widely used thermo-responsive polymer

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• -soluble polymers [109]. For instance, PNIPAM is a thermo-responsive polymer, which has a lower critical solution temperature (LCST) of 32 °C. Above the LCST, individual polymer chains switch from a swollen coil configuration to a collapsed globular one, providing a nano-environment that is suitable for

Block copolymers from ionic liquids for the preparation of thin carbonaceous shells

• Sadaf Hanif,
• Bernd Oschmann,
• Dmitri Spetter,
• Muhammad Nawaz Tahir,
• Wolfgang Tremel and
• Rudolf Zentel

Beilstein J. Org. Chem. 2017, 13, 1693–1701, doi:10.3762/bjoc.13.163

• with unique properties. Alternatively, it is possible to coordinate low molar mass ionic liquids to polymers by complexation of their anions to cyclodextrin side chains. This can have an influence on their lower critical solution temperature (LCST) [10][11]. Beside their use as organic solvent, they

Conjugates of methylated cyclodextrin derivatives and hydroxyethyl starch (HES): Synthesis, cytotoxicity and inclusion of anaesthetic actives

• Lisa Markenstein,
• Antje Appelt-Menzel,
• Marco Metzger and
• Gerhard Wenz

Beilstein J. Org. Chem. 2014, 10, 3087–3096, doi:10.3762/bjoc.10.325

• than the corresponding monomeric CD derivatives. Since the binding potentials of these CD conjugates were very high, they are promising candidates for new oral dosage forms of anaesthetic actives. Keywords: anaesthetics; complexation; cyclodextrin; LCST; lower critical solution temperature; midazolam

• conjugates, listed in Table 1, were clearly soluble in water at ambient conditions but most of them precipitated at elevated temperatures. This so-called lower critical solution temperature is typical for alkylated neutral polysaccharides and attributed to increasing hydrophobic interactions with increasing

Synthesis of uniform cyclodextrin thioethers to transport hydrophobic drugs

• Lisa F. Becker,
• Dennis H. Schwarz and
• Gerhard Wenz

Beilstein J. Org. Chem. 2014, 10, 2920–2927, doi:10.3762/bjoc.10.310

• derivatives 2, 3 and 4 were indeed highly soluble in water at 25 °C but upon heating the clear solutions turned turbid at a certain temperature and the compounds precipitated. The observed phase separation at the so-called lower critical solution temperature (LCST) is typical for uncharged polymeric

Influence of cyclodextrin on the UCST- and LCST-behavior of poly(2-methacrylamido-caprolactam)-co-(N,N-dimethylacrylamide)

• Alexander Burkhart and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 1951–1958, doi:10.3762/bjoc.10.203

• synthesized from methacryloyl chloride (3) and racemic α-amino-ε-caprolactam (2). Copolymerization of 4 with N,N-dimethylacrylamide (5) was carried out by a free-radical mechanism using 2,2’-azobis(2-methylpropionitrile) (AIBN) as an initiator. The new copolymers show a lower critical solution temperature

• tissue engineering [1][2][3]. Especially polymers having a lower critical solution temperature (LCST) in water, like poly(N-isopropylacrylamide) or modified poly(N-vinylpyrrolidone) are extensively described in literature [4][5]. Below the critical temperature (TC) these polymers are soluble and they

An economical and safe procedure to synthesize 2-hydroxy-4-pentynoic acid: A precursor towards ‘clickable’ biodegradable polylactide

• Quanxuan Zhang,
• Hong Ren and
• Gregory L. Baker

Beilstein J. Org. Chem. 2014, 10, 1365–1371, doi:10.3762/bjoc.10.139

• family of water-soluble and temperature responsive biodegradable PLA material with tunable lower critical solution temperature (LCST) in a range from 25 to 65 °C was obtained after ‘click’ grafting with a mixture of alkyl and PEG azides. Starting from the same precursor 1 [18], Yu and coworkers have

End-group-functionalized poly(N,N-diethylacrylamide) via free-radical chain transfer polymerization: Influence of sulfur oxidation and cyclodextrin on self-organization and cloud points in water

• Sebastian Reinelt,
• Daniel Steinke and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 680–691, doi:10.3762/bjoc.10.61

• methylated β-cyclodextrin (RAMEB-CD). Additionally, the influence of the oxidation of the incorporated thioether linkages on the cloud point is investigated. The resulting hydrophilic sulfoxides show higher cloud point values for the lower critical solution temperature (LCST). A high degree of

• functionalization is supported by 1H NMR-, SEC-, FTIR- and MALDI–TOF measurements. Keywords: chain-transfer polymerization; cyclodextrins; end-group functionalization; host–guest interaction; lower critical solution temperature (LCST); poly(N,N-diethylacrylamide); Introduction Supramolecular chemistry was first

• temperature are widely investigated [13]. Within this group of materials, thermosensitive water-soluble polymers, possessing a lower critical solution temperature (LCST), have attracted much attention in several studies within the last decades [13][14][15][16][17]. The nature of the end-group of a short chain

Oligomeric epoxide–amine adducts based on 2-amino-N-isopropylacetamide and α-amino-ε-caprolactam: Solubility in presence of cyclodextrin and curing properties

• Julian Fischer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 2803–2811, doi:10.3762/bjoc.9.315

• diglycidyl ether to give novel oligomeric thermoresponsive epoxide–amine adducts. These oligomers exhibit a lower critical solution temperature (LCST) behavior in water. The solubility properties were influenced with randomly methylated β-cyclodextrin (RAMEB-CD) and the curing properties of the amine–epoxide

• polymers exhibit a lower critical solution temperature (LCST) behavior in water [1][2]. Below the critical temperature (Tc) these substances are completely soluble in water, whereas above the Tc they precipitate. Thereby, hydrogen bonds between polymer chains and water molecules in cold water lead to good

Cyclodextrin-induced host–guest effects of classically prepared poly(NIPAM) bearing azo-dye end groups

• Gero Maatz,
• Arkadius Maciollek and
• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1929–1935, doi:10.3762/bjoc.8.224

• [4-(4’-aminophenylazo)phenyl]amine. This dye-end-group-labeled polymer showed acidochromic effects, depending on the pH and the presence of randomly methylated β-cyclodextrin (RAMEB-CD). Also higher cloud-point values for the lower critical solution temperature (LCST) in the presence of RAMEB-CD were

• techniques. Water-soluble polymers, which exhibit a lower critical solution temperature (LCST), e.g., many poly(N-alkylacrylamides), have found numerous practical applications in waterborne smart materials such as bioactive surfaces, selective bioseparation, or hyperthermia-induced drug delivery [14

Supramolecular hydrogels formed from poly(viologen) cross-linked with cyclodextrin dimers and their physical properties

• Yoshinori Takashima,
• Yang Yuting,
• Miyuki Otsubo,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2012, 8, 1594–1600, doi:10.3762/bjoc.8.182

• reports of supramolecular complexes with cyclodextrin (CD) dimers. A supramolecular hydrogel, which was constructed by the formation of an inclusion complex between the copolymer with an adamantyl group and CD dimer, showed a lower critical solution temperature (LCST) [11]. Another report indicated that

Influence of cyclodextrin on the solubility of a classically prepared 2-vinylcyclopropane macromonomer in aqueous solution

• Helmut Ritter,
• Jia Cheng and
• Monir Tabatabai

Beilstein J. Org. Chem. 2012, 8, 1528–1535, doi:10.3762/bjoc.8.173

• DLS was about 4.1 nm. DSC measurement showed the glass-transition temperature (Tg) at about 123.5 °C. Due to the hydrophilicity of the amino end groups of 3 a typical LCST (lower critical solution temperature) was observed close to that of unmodified poly(NiPAAm) at about 33.4 °C (Figure 2). Via

Chiral recognition of ephedrine: Hydrophilic polymers bearing β-cyclodextrin moieties as chiral sensitive host molecules

• Sabrina Gingter and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 1516–1519, doi:10.3762/bjoc.7.177

• reported recently, the CD containing NIPAAm copolymer 1 exhibits lower critical solution temperature (LCST) behavior in water [23]. As expected, the supramolecular system 2 turned out to be soluble in cold water only below the LCST of 32 °C. However, due to the presence of relatively hydrophilic ephedrine

Chiral recognition of macromolecules with cyclodextrins: pH- and thermosensitive copolymers from N-isopropylacrylamide and N-acryloyl-D/L-phenylalanine and their inclusion complexes with cyclodextrins

• Sabrina Gingter,
• Ella Bezdushna and
• Helmut Ritter

Beilstein J. Org. Chem. 2011, 7, 204–209, doi:10.3762/bjoc.7.27

• -isopropylacrylamide (NIPAAm). The resulting copolymers 3D and 3L exhibit a lower critical solution temperature (LCST) of 25 °C. As a further benefit, the presence of a free carboxylic group in the copolymer system gives a high sensitivity to the pH value in respect to the LCST value. The enantioselective recognition

Hybrid biofunctional nanostructures as stimuli-responsive catalytic systems

• Gernot U. Marten,
• Thorsten Gelbrich and
• Annette M. Schmidt

Beilstein J. Org. Chem. 2010, 6, 922–931, doi:10.3762/bjoc.6.98

• , biocompatibility, and a tunable lower critical solution temperature (LCST) in water. The phase separation can alternatively be initiated by magnetic heating caused by magnetic losses in ac magnetic fields. The immobilization of porcine pancreas trypsin to the core–shell nanoparticles results in highly active

Free radical homopolymerization of a vinylferrocene/cyclodextrin complex in water

• Helmut Ritter,
• Beate E. Mondrzik,
• Matthias Rehahn and
• Markus Gallei

Beilstein J. Org. Chem. 2010, 6, No. 60, doi:10.3762/bjoc.6.60

• scanning calorimetry (DSC), and lower critical solution temperature (LCST) measurements. Keywords: cyclodextrin; free radical polymerization; polyvinylferrocene; vinylferrocene; Introduction Since its discovery in 1951, ferrocene [1] and its derivatives and their applications have been the subject of

• and precipitated (c). Lower critical solution temperature of PVFc-co-P(NiPAAM) 7 (1:20) (solid line): 17 °C and complexed NiPAAM with additional methyl-β-CD (dashed line): 19 °C. Homopolymerization of vinylferrocene 1. Copolymerization of vinylferrocene 1 with NiPAAM 5 (1:20).