Design and synthesis of a photoswitchable guanidine catalyst

• Philipp Viehmann and
• Stefan Hecht

Beilstein J. Org. Chem. 2012, 8, 1825–1830, doi:10.3762/bjoc.8.209

• rac-lactide in order to explain the findings. Keywords: azobenzenes; guanidines; molecular switches; organocatalysis; photochromism; ring opening polymerization; Introduction The macroscopic properties of a given polymer, e.g., the glass-transition temperature, morphology, density and tensile

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

• Narcisa Marangoci,
• Rodinel Ardeleanu,
• Laura Ursu,
• Constanta Ibanescu,
• Maricel Danu,
• Mariana Pinteala and
• Bogdan C. Simionescu

Beilstein J. Org. Chem. 2012, 8, 1610–1618, doi:10.3762/bjoc.8.184

• decreases when their glass-transition temperature (Tg) increases [23]. In this respect, we have synthesized ILs based on polydimethylsiloxane with imidazolium salt brushes (PDMS-Im/S) with low Tg values in order to avoid a macroscopic phase separation in a mixture of ILs and CD-polydimethylsiloxane

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

• polymerization of 5. In addition, the product has only shown one glass-transition temperature Tg at 133.7 °C. This confirmed the formation of a copolymer 8. If two homopolymers coexist, two glass-transition temperatures should be measured. Both products 6 and 8 show the LCST behavior, respectively (Figure 2

Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone

• Miroslav Mrsevic,
• David Düsselberg and
• Claudia Staudt

Beilstein J. Org. Chem. 2012, 8, 776–786, doi:10.3762/bjoc.8.88

• ) sulfide (4,4′-diaminodiphenyl sulfide, 4,4′-SDA) groups, were used for the synthesis of novel (co)polyimides in this work [25]. In order to investigate structural effects of the DABA groups on the glass-transition temperature, molecular weight, transparency and water sorption, both polymers 6FDA-4,4′-SDA

• all synthesized (co)polyimides, as expected. Gibbs et al. already showed in 1958, that the glass-transition temperature is affected by the rigidity of the polymer backbone [30] and that the glass-transition temperature of a copolymer is a linear function of the composition of the copolymer [31

• single bonds than both of the sulfur-containing diamines, and this therefore improves the rigidity of the polymer chain. Additionally the carboxyl groups of the DABA can lead to hydrogen bonding in the polymer chains, which additionally increases the glass-transition temperature. For further verification

Imidazole as a parent π-conjugated backbone in charge-transfer chromophores

• Jiří Kulhánek and
• Filip Bureš

Beilstein J. Org. Chem. 2012, 8, 25–49, doi:10.3762/bjoc.8.4

• stability of alignment of the chromophore. The glass transition temperature (Tg) and the decomposition temperature (TD) are the most widely provided parameters of polymer physical stability. The polar order of the polymer (centrosymmetry removal) is usually achieved by the electric-field, thermal (Tp) and

Novel carbazole–pyridine copolymers by an economical method: synthesis, spectroscopic and thermochemical studies

• Aamer Saeed,
• Madiha Irfan and
• Shahid Ameen Samra

Beilstein J. Org. Chem. 2011, 7, 638–647, doi:10.3762/bjoc.7.75

• . For DSC, the samples were first heated to melting, then cooled to the glassy state and reheated to determine the glass transition temperature (Tg). A representative DSC graph is shown for P1a in Figure 5. Tg is calculated from the second heating curve. As it can be seen from the graph, Tg for the

Formation of epoxide-amine oligo-adducts as OH-functionalized initiators for the ring-opening polymerization of ε-caprolactone

• Julia Theis and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 938–944, doi:10.3762/bjoc.6.105

• calorimetry (DSC) curve of compound 4 shows a glass transition temperature (Tg) at 63 °C. The low molecular weight epoxide-amine adduct 4 is soluble, e.g., in tetrahydrofuran (THF), methanol, chloroform but insoluble in n-hexane and water. We also carried out the above described one-pot reaction in THF as

• a temperature range between −40 and 120 °C at a heating rate of 10 K min−1. For calibration, standard tin, indium and zinc samples were used. Three heating cycles were conducted. The glass-transition temperature (Tg) values are reported as the average of the second and the third heating cycle using

Synthesis and crystal structures of multifunctional tosylates as basis for star-shaped poly(2-ethyl-2-oxazoline)s

• Richard Hoogenboom,
• Martin W. M. Fijten,
• Guido Kickelbick and
• Ulrich S. Schubert

Beilstein J. Org. Chem. 2010, 6, 773–783, doi:10.3762/bjoc.6.96

• hydrophobic; and from hard materials, with a high glass transition temperature via crystalline and chiral polymers [7], to soft materials, with a very low glass transition temperature [8][9]. The synthesis of star-shaped poly(2-oxazoline)s has been reported using a range of multifunctional electrophilic

Novel multi-responsive P2VP-block-PNIPAAm block copolymers via nitroxide-mediated radical polymerization

• Cathrin Corten,
• Katja Kretschmer and
• Dirk Kuckling

Beilstein J. Org. Chem. 2010, 6, 756–765, doi:10.3762/bjoc.6.89

• P2VP content, the phase transition temperature shifted to lower temperatures (e.g., 26 °C for P2VP114-block-PNIPAAm180). DLS measurements of the block copolymers underlined the multi-responsive and schizophrenic behavior in aqueous solutions. DSC measurement of the glass transition temperature revealed

• . DSC measurements were carried out with a Mettler-Toledo DSC 30 to determine the glass transition temperature (Tg) of the block copolymers (heating rate 10 °C/min) and with a TA Instruments DSC 2290 to measure the phase transition temperature (Tc) (heating rate of 5 °C/min) as an average of 4 cycles

Chromo- and fluorophoric water-soluble polymers and silica particles by nucleophilic substitution reaction of poly(vinyl amine)

• Katja Hofmann,
• Ingolf Kahle,
• Frank Simon and
• Stefan Spange

Beilstein J. Org. Chem. 2010, 6, No. 79, doi:10.3762/bjoc.6.79

• . The IR absorption of the aromatic C=C units occurs at ca. = 1665 cm−1 which appear to be overlapped by N–H deformation vibration bands. The presence of the C≡N stretching band at = 2221 cm−1 confirms the existence of the organo-substituted fluorophore. The glass transition temperature Tg is an

• important parameter for polymers, which indicates the transition of the amorphous phase of the polymer from its rubbery to its glassy state (and vice versa). Pure PVAm shows a Tg of 103 °C. The glass transition temperature is a function of chain flexibility. Because of the presence of hydrogen-bond donor

• individual polymer chains, resulting in a decreased glass transition temperature. Synthesis and characterization of the hybrid material As can be seen from Scheme 3, carbonitrile 1 was adsorbed from its dichloromethane solution onto carefully dried silica particles (Kieselgel 60, Merck). The 1-loaded silica

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

• polyvinylferrocene 3 had a glass transition temperature (Tg) of 145 °C. FT-IR (film) 3: 2902 cm−1 (–C–H), 1643 cm−1 (–C=C), 1452 cm−1 (CH2), 1153, 1033 cm−1 (–C–O), 1082 cm−1 (C–O–C), 964, 758, 702 cm−1 (=C–H); 1H NMR: (500 MHz, DMSO-d6, 298 K) 3: δ (ppm) = 1.83 (CH2), 3.10–3.31 (14H, 5-H) 3.45–3.65 (28H, 6-H) 4.11

Synthesis, characterization and photoinduced curing of polysulfones with (meth)acrylate functionalities

• Cemil Dizman,
• Sahin Ates,
• Lokman Torun and
• Yusuf Yagci

Beilstein J. Org. Chem. 2010, 6, No. 56, doi:10.3762/bjoc.6.56

• -containing polymers [32]. Major degradation of the oligomers began at around 400 °C. The overall thermal stability of the polymers is similar. As can be seen from Figure 6, the glass transition temperature (Tg) of the acrylate macromonomer is more than 20 °C higher than that of its precursor polymer because