Photoinitiators and photoinitiation, 16. The photodecomposition of some 1‐phenyl‐3‐sulphonyloxy‐1,2‐propanediones

The photodecomposition of the title compounds is studied by ESR spectroscopy using a spin‐trapping agent. The radicals observed indicate the breakdown of the title compounds and the simultaneous generation of sulphonic acid. Confirmative evidence for the photoinduced release of sulphonic acid is provided by the acid‐catalysed crosslinking of a melamine resin.     

Crystallization of the polyethylene block in polystyrene‐b‐polyethylene‐b‐polycaprolactone triblock copolymers, 1. Self‐nucleation behavior

The self‐nucleation of branched polyethylene chains of different degrees of chain mobility was studied. The polyethylene block (PE block) within poly(styrene‐b‐ethylene‐b‐caprolactone) triblock copolymers (SEC) of varying compositions was studied. Differential scanning calorimetry was used to determine the self‐nucleation domains as a function of the self‐nucleation temperature (T_s). The self‐nucleation behavior of PE chains within SEC block copolymers was found to be anomalous in comparison to the classical self‐nucleation behavior exhibited by homopolymers. When the degree of chain constraint is high, as in the case where the SEC copolymer only contains 15% of PE, domain II (only self‐nucleation domain) completely disappears and annealing can take place before self‐nucleation occurs. This means that chain constraint complicates the self‐nucleation process and this situation persists until, upon decreasing the self‐nucleation temperature (T_s), annealing has generated crystals that are big enough to act as self‐nuclei for the less restricted portions of the chain. If the PE content in the copolymer is very low (15%), two crystal populations can be distinguished. This may reflect the differences in diffusion of the PE chain segments close to the interfaces with the other two blocks and those segments that are close to the middle of the PE block. The influence of chain constraint on determining the difficulty of the chains to self‐nucleate was further explored using a crosslinked low‐density polyethylene (XLDPE). In this case, crosslinking junctions instead of covalent links with other blocks restrict chain mobility. Nevertheless, a similar difficulty in self‐nucleation was found as in the case of the PE block within SEC triblock copolymers in contrast to neat LDPE, a polymer that exhibited the classical self‐nucleation behavior with the usual three domains.     

3‐Butyl‐2‐yl‐ and Propargyl Cholesteryl Carbonates. Chiroptical and Liquid Crystalline Properties of their Polymers

Novel chiral acetylene monomers containing cholesteryl groups, (R)‐3‐butyn‐2‐yl cholesteryl carbonate ( 1 ), (S)‐3‐butyn‐2‐yl cholesteryl carbonate ( 2 ), and propargyl cholesteryl carbonate ( 3 ) were synthesized and polymerized with (nbd)Rh⁺[η⁶‐C₆H₅B^?(C₆H₅)₃] to give the corresponding polymers with number‐average molecular weights of 32 900–97 000 in 84–85% yields. Circular dichroism spectroscopic studies revealed that poly( 1 ) and poly( 2 ) predominantly took one‐handed helical structure in CHCl₃ and THF. The helical conformation was stable to heat and to addition of MeOH. The copolymerization of 1 and 2 was carried out with the rhodium catalyst to afford copolymers with number‐average molecular weights ranging from 53 400 to 88 700 in 83–98% yields. The copolymer with a large diastereomeric excess showed a large specific rotation and an intense Cotton effect in THF, indicating that the predominance of one‐handed helicity was high. Poly( 1 ₅₀‐co‐ 2 ₅₀) showed lyotropic liquid crystalline property.

     

PD‐1 modulates steady‐state and infection‐induced IL‐10 production in vivo

Programmed death‐1 (PD‐1) plays an important role in mediating immune tolerance through mechanisms that remain unclear. Herein, we investigated whether PD‐1 prevents excessive host tissue damage during infection with the protozoan parasite, Toxoplasma gondii. Surprisingly, our results demonstrate that PD‐1‐deficient mice have increased susceptibility to T. gondii, with increased parasite cyst counts along with reduced type‐1 cytokine responses (IL‐12 and IFN‐γ). PD‐1^?/? DCs showed no cell intrinsic defect in IL‐12 production in vitro. Instead, PD‐1 neutralization via genetic or pharmacological approaches resulted in a striking increase in IL‐10 release, which impaired type‐1‐inflammation during infection. Our results indicate that the absence of PD‐1 increases IL‐10 production even in the absence of infection. Although the possibility that such increased IL‐10 protects against autoimmune damage is speculative, our results show that IL‐10 suppresses the development of protective Th1 immune response after T. gondii infection.     

Ring‐Opening Homo‐ and Copolymerization of Cis/Trans‐3‐oxa‐4‐oxobicyclo‐ and Cis/Trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane

Ring‐opening polymerization of the bicyclic lactone mixture 2 , cis/trans‐3‐oxa‐4‐oxo‐ and cis/trans‐4‐oxa‐3‐oxobicyclo[5.4.0]undecane with Sn(Oct)₂ as a catalyst was investigated for the first time (Scheme 1 ). The lactones were obtained by Baeyer–Villiger oxidation of cis/trans‐2‐decalone 1 (Scheme 2 ). Additionally, copolymerization of 2 with ε‐caprolactone in different ratios was performed. GPC measurements and ¹H NMR spectroscopy proved that 2 was quantitatively incorporated into the polymer, leading to polycaprolactone with cyclohexane moieties in its backbone. values were up to 25 000 with ≤ 2.4. DSC measurements revealed a linear dependence of the melting points and the glass transition temperatures of the polymers on the feed of the bicyclic lactone 2 . Additionally, the time dependence of the cis/trans ratio of the residual monomers was followed during the course of polymerization reaction by gas chromatography. The crystallinity of the resulting copolymers was investigated via polarization microscopy. Finally, it was shown that the mixture of 2 with ε‐caprolactone could be selectively polymerized with lipase. Only ε‐caprolactone was converted, while 2 remained unreacted in the residue.

     

Synthesis and properties of fluorinated polyimides, 2. Derived from novel 2,6‐bis(3′‐trifluoromethyl‐p‐aminobiphenyl ether)pyridine and 2,5‐bis(3′‐trifluoromethyl‐p‐aminobiphenyl ether)thiophene

Novel diamine monomers, 2,6‐bis(3′‐trifluoromethyl‐p‐aminobiphenyl ether)pyridine (TABP) and 2,5‐bis(3′‐trifluoromethyl‐p‐aminobiphenyl ether)thiophene (TABT) have been synthesized, which lead to a number of novel fluorinated polyimides by thermal imidization routes when reacted with different commercially available dianhydrides like pyromellitic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA) or 2,2‐bis(3,4‐dicarboxyphenyl) hexafluoropropane (6FDA). The polyimides ABTP/6FDA and ABTT/6FDA are soluble in several organic solvents such as N,N‐dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc) and tetrahydrofuran (THF). The polyimide ABTP/PMDA is only soluble in N‐methylpyrollidone (NMP) whereas ABTT/PMDA is insoluble in all solvents. The polyimides ABTP/6FDA (2c) and ABTT/6FDA (3c) exhibited number‐average molecular weight 32 940 (polydispersity index (PDI), 1.97) and 24 760 (PDI, 1.87) respectively. These polyimide films have low water absorption rate 0.3–0.9% and low dielectric constant 2.92–3.29 at 1 MHz. These polyimides showed very high thermal stability even up to 532 °C for 5% weight loss in synthetic air and glass transition temperature up to 287 °C (by DSC) in nitrogen. All polyimides formed tough transparent films, with tensile strength up to 115 MPa, a modulus of elasticity up to 2.91 GPa and elongation at break up to 12% depending upon the exact repeating unit structure.

TGA thermograms of the thiophene ring poly(ether imide)s.     

Synthesis and 7Li Ion Dynamics in Polyarylene‐Ethersulfone‐Phenylene‐Oxide‐Based Polymer Electrolytes

A new block‐co‐polymer based on poly(arylene ether sulfone) and nitrile‐functionalized poly(phenylene oxide) is prepared via polycondensation. Upon swelling with Li triflate dispersed in succinonitrile, a polymer electrolyte suitable for application in secondary Li ion batteries is obtained, which at temperatures above 313 K exhibits conductivities of 10^?4–10^?3 S cm^?1. The presence of distinct coordination modes of the Li ions (not discernible from inspection of ⁷Li chemical shifts) is revealed based on a dynamic contrast identified from a distribution of transverse relaxation times. Three relaxation components reflecting polymer‐bound, partially and fully solvated Li ion species are identified on the basis of Carr–Purcell–Meiboom–Gill NMR data after inverse Laplace transformation and multiexponential relaxation analysis toolkit analysis thus highlighting the versatility of the applied methods.

     

Association between polymorphisms in catechol‐O‐methyltransferase (COMT) and cocaine‐induced paranoia in European‐American and African‐American populations

Catechol‐O‐methyltransferase (genetic locus, COMT) is a major enzyme involved in catecholamine metabolism and has been associated with numerous psychiatric phenotypes. We studied COMT SNPs and haplotypes in cocaine‐induced paranoia (CIP) in African‐American (AA) and European‐American (EA) populations. We genotyped 17 SNPs across the COMT locus in 319 AA pedigrees (848 individuals) and 302 EA pedigrees (707 individuals). Family‐controlled association analyses were conducted using FBAT. We found SNP rs737865 to be nominally significantly associated in the AA family population (P = 0.05). In EAs, the best‐known marker, rs4680 (Val158Met), was nominally significant in additive models (P = 0.03). SNP rs174696 also showed nominal significance in additive models (P = 0.02). We considered the three SNPs (rs737866–rs4680–rs174696) together in haplotype analysis in both family populations, using HBAT. The A–A–T haplotype was significantly associated with CIP in EAs (Z = 2.845; P = 0.0044, global P = 0.020). We then studied COMT SNPs in an additional 738 AA and 404 EA unrelated cocaine dependent individuals with and without paranoia. The A–A–T haplotype was significantly associated to CIP in the AA unrelated population (P = 0.0015). Two haplotypes, A–G–C and A–A–C, were significant in the EA unrelated population (P = 0.001 and 0.0003). We also identified rs4680 and three other SNPs, rs933271, rs5993883, and rs740603, as potentially functional variants, as predicted by a signature of positive selection in unrelated EAs and AAs. Based on our robust family‐controlled and unrelated‐affected analyses, we conclude that COMT is associated with CIP, possibly as a result of its role in the metabolism of dopamine and norepinephrine. © 2011 Wiley‐Liss, Inc.     

Polymerization of Lactides and Lactones, 8. Study on the Ring‐Opening Polymerization of 3‐Phenyl‐ε‐caprolactone and 5‐Phenyl‐ε‐caprolactone

Ring‐opening polymerization of 3‐phenyl‐ε‐caprolactone (3‐ph‐CL) and 5‐phenyl‐ε‐caprolactone (5‐ph‐CL) by tin(II) salt, Al(OⁱPr)₃ and CpNa has been studied; 3‐ph‐CL cannot be initiated by Al(OⁱPr)₃. Polymerization of 5‐ph‐CL initiated with Al(OⁱPr)₃ in toluene at 15°C yielded a polymer of a predictable molecular weight and a narrow molecular weight distribution. 3‐ph‐CL and 5‐ph‐CL can be polymerized by initiating with tin(II) salt, and CpNa. In CpNa‐based polymerization, high molecular weight P(3‐ph‐CL) and P(5‐ph‐CL) were obtained. DSC studies indicate that P(5‐ph‐CL) is an amorphous material, exhibiting a rubber state at room temperature. Compared with PCL, the glass transition temperature of P(3‐ph‐CL) and P(5‐ph‐CL) is higher (–60°C), in contrast to the melting temperature, which is higher for PCL. These new monomers give a route to novel aliphatic polyesters.     

Stereocomplex‐ and Homo‐Crystallization and Phase‐Transition Behavior of Relatively High‐Molecular‐Weight Linear One‐ and Two‐Armed and Star‐Shaped Four‐Armed Poly(l‐lactide)/Poly(d‐lactide) Blends

Relatively high‐molecular‐weight linear one‐ and two‐armed and star‐shaped four‐armed poly(l ‐lactide) and poly(d ‐lactide) are synthesized and the multiplicate effects of arm‐number (branching architecture, coinitiator moiety), crystallization temperature (T _c), and number‐average molecular weight (M _n) on stereocomplex (SC)‐ and homo‐crystallization and phase‐transition behavior are investigated. For nonisothermal and isothermal crystallization, in addition to SC crystallites, homo‐crystallites are formed in the blends with higher M _n values, irrespective of arm number. For isothermal crystallization, the transition T _c ranges below which in addition to SC crystallites, homo‐crystallites are formed depended on M _n per one arm‐determining melting temperature or thickness of homo‐crystallites. The transition M _n ranges above which in addition to SC crystallites, homo‐crystallites are formed are not affected by arm number. The high molecular weight disturbs the change of crystalline growth mechanism of one‐ and two‐armed blends, whereas the branching architecture inhibits the change of crystalline growth mechanism of four‐armed blends.     

Polylactones, 45. Homo‐ and Copolymerizations of 3‐Methylmorpholine‐2,5‐dione Initiated With a Cyclic Tin Alkoxide

Morpholine‐2,5‐dione and D ,L ‐3‐methylmorpholine‐2,5‐dione were polymerized with 2,2‐dibutyl‐2‐stanna‐1,3‐dioxepane (DSDOP) as initiator with variation of time and monomer/initiator (M/I)‐ratio. For comparison a few polymerizations were initiated with Sn(II) 2‐ethylhexanoate. The DSDOP initiated polymerizations gave slightly higher molecular weights, but the molecular weights were rather low in all cases and did not parallel the M/I‐ratio. Furthermore, D ,L ‐3‐methylmorpholine‐2,5‐dione was copolymerized with ε‐caprolactone (ε‐CL) or with L ‐lactide. ¹³C NMR spectra proved the formation of nearly random sequences. Therefore, the 1 : 1 copolymers were amorphous. Higher feed ratios of ε‐CL or L ‐lactide yielded higher molecular weights (at constant M/I‐ratio) and they yielded crystalline copolyesters as evidenced by DSC‐measurements.