Enzymes in polymer chemistry, 8 Chemoenzymatic synthesis of polymerizable 11-methacryloyl-aminoundecanoic ester of 1- and 3-O-methyl-α-D-glucose in 6-O-position

The paper describes the regioselective esterification of a glucopyranoside and glucose derivative with 11-methacryloylaminoundecanoic acid in the presence of a lipase from Candida antarctica. The obtained modified sugar derivatives 6-O-(11-methacryloylaminoundecanoyl)-1-O-methyl-α-D -glucopyranoside (3 a) and 6-O-(11-methacryloylaminoundecanoyl)-3-O-methyl-α-D -glucopyranose (3 b) were polymerized radically with AIBN as initiator.     

Cyclodextrins in polymer synthesis: free radical polymerisation of cyclodextrin complexes of cyclohexyl and phenyl methacrylate in aqueous medium

The polymerisation mechanism of 2,6-dimethyl-β-cyclodextrin (Me₂-β-CD) complexes of phenyl methacrylate ( 1 ) and cyclohexyl methacrylate ( 2 ) is described. The polymerisation of the complexes 1 a and 2a was carried out in water with potassium peroxodisulfate/potassium hydrogensulfite as initiator. The unthreading of the Me₂-β-CD during the polymerisation led to water-insoluble poly(phenyl methacrylate) ( 1b ) and poly(cyclohexyl methacrylate) ( 2b ). By comparison, analogously prepared polymers from uncomplexed monomers 1 and 2 in homogeneous organic solvent (THF) with AIBN as radical initiator showed significantly lower viscosities and were obtained in lower yields in both cases.     

Tantalcluster in oxidischer Matrix – Synthese und Strukturen der gemischtvalenten Oxotantalate M2–δTa15O32 (M = K,Rb (δ = 0); M = Sr (δ = 0.15), Ba (δ = 0.12))

Tantalum Cluster in an Oxidic Matrix – Synthesis and Structures of Mixed-Valence Oxotantalates M_2–δTa₁₅O₃₂ (M = K, Rb (δ = 0); M = Sr (δ = 0.15), Ba (δ = 0.12)) The mixed-valent oxides Sr_1.85Ta₁₅O₃₂ ( 1 ), Ba_1.88Ta₁₅O₃₂ ( 2 ), K₂Ta₁₅O₃₂ ( 3 ), Rb₂Ta₁₅O₃₂ ( 4 ) were prepared from appropriate mixtures of Ta₂O₅, tantalum and the corresponding carbonate at 1520–1670 K in sealed tantalum tubes. According to X-ray single crystal structure analyses the oxides crystallize in the space group R3¯, Z = 1. The lattice parameters in the hexagonal setting are a = 777.36(11), c = 3516.2(7) pm for 1 , a = 778.87(11), c = 3548.1(7) pm for 2 , a = 780.7(2), c = 3573.1(11) pm for 3 , and a = 781.90(11), c = 3593.0(7) pm for 4 . The oxide ions form a defect dense packing with the layer sequence chhhh. Anti-cuboctahedral sites are completely occupied by the alkali metal cations. The alkaline earth cations occupy 92 to 94% of such sites; they are displaced from the centres. Smaller voids are located in the centres of the cuboctahedral Ta₆O₁₂ clusters forming the characteristic structural unit of these low-valent oxotantalates. In case of 3 and 4 the clusters have 13 electrons, in case of 1 and 2 they have close to 15 electrons available for Ta–Ta-bonding. Moreover, the structures of the alkali and alkaline earth metal compounds differ notably with respect to the spectrum of Ta–O and Ta–Ta distances in the Ta₃O₁₃ octahedra triples forming another characteristic structural unit for these oxides. Such differences are traced back to distinct local charge balances for the uni- and divalent cations. The oxides 2 , 3 are semiconductors with band gaps ranging from 130 to 360 meV.     

Reductive Cross-Coupling of a Vinyl Thianthrenium Salt and Secondary Alkyl Iodides

We report the first reductive vinylation of alkyl iodides. The reaction uses a vinyl thianthrenium salt, a palladium catalyst, and an alkyl zinc intermediate formed in situ to trap the L_nPd^II(vinyl) complex formed after oxidative addition before it undergoes undesired homocoupling to form butadiene.     

Topologically unique side-chain polyrotaxanes based on triacetyl-β-cyclodextrin and a poly(ether sulfone) main chain

The synthesis and NMR-spectroscopical characterization of the topological arrangements of new side-chain polyrotaxanes (3a) bearing about 80% of peracetylated cyclodextrins in the side-chains of a functionalized poly(ether sulfone) is described. The characterizations have been conducted in relation to a similar model compound bearing no cyclodextrins (3b) . The results strongly indicate that the cyclodextrins are uniformly located on the side chains, with the bigger opening over the aromatic anilide components of the barrier group. The glass transition temperature (T_g) of the polyrotaxane 3a is in the region of 143°C, which is significantly higher than that of the model polymer 3b having a value of 111°C.     

Polymeric mesoions, 3. Synthesis of polymeric mesoionic 1,3-diazinium-olates via polymer analogous modification of a polythiourea from m-phenylenediamine and p-phenylene diisothiocyanate

Mesoionic poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bis(5-decyl-2-decylthio-4,6-dioxo-1,3-diazine)) ( 6 ) was prepared by cyclisation of the isothiourea component of poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bis(2-decylisothiourea)) ( 4 ) with decylmalonic acid (5) by use of dicyclohexylcarbodiimide (DCC). Polymer 4 was obtained by polymer analogous alkylation of poly(1,1′-(1,3-phenylene)-3,3′-(1,4-phenylene)-bisthiourea) ( 3 ). For comparison of spectroscopic data, 5-butyl-2-propylthio-4,6-dioxo-1,3-diphenyl-1,3-diazine ( 9 ) was synthesized as low molecular weight model compound.     

Cyclodextrins in Polymer Synthesis: Crosslinking Water‐Soluble Unsaturated Polyester Resins Using a Cyclodextrin/Styrene Complex in Aqueous Medium

A new method was developed to crosslink water‐soluble unsaturated polyester resins prepared from maleic anhydride and poly(ethylene glycol) in water as the solvent. Crosslinking was carried out with various molar ratios of the host‐guest complex consisting of styrene as the guest and methylated β‐cyclodextrin as the host. Polymerizations were performed in water with K₂S₂O₈/Na₂S₂O₅ as free radical initiator at 25 °C. Thermal properties of the networks obtained depend on the amount of styrene incorporated into the polymer.

Acceleration effect of me‐β‐CD during crosslinking of an unsaturated polyester with styrene in water: (a) monomer complexed with me‐β‐CD, and (b) with uncomplexed monomer.