Syntheses of polymers having imidazolidinone rings

4,4′-Diaminodiphenylmethane and 1-(p-chlorophenyloxycarbonyl)aziridine gave 1,1′-(methylene-di-p-phenylene)-bis-(1,3-imidazolidine-2-one). The bis-imidazolidinone reacted with formaldehyde or acrylonitrile to give 1,1′-(methylene-di-p-phenylene)-bis-(3-hydroxymethyl-1,3-imidazolidine-2-one) or 1,1′-(methylene-p-phenylene)-bis-[3-(2-cyanoethyl)-1,3-imidazolidine-2-one] respectively. The bis-methylol derivative gave a polycondensation product on standing in dichloroacetic acid. The dicarboxylic acid which was obtained by treating the bis-cyanoethyl derivative with concentrated hydrochlorie acid gave high molecular polyamides having imidazolidinone rings in the polymer chain by the reaction with hexamethylene diamine or m-xylylene diamine.     

Synthesis and properties of novel soluble polyimides having an unsymmetric spiro tricyclic dianhydride unit

A novel spiro trialicyclic dianhydride, rel[1S,5R,6R]‐3‐oxabicyclo[3.2.1]octane‐2,4‐dione‐6‐spiro‐3′‐(tetrahydrofuran‐2′,5′‐dione) ( DAn ) was synthesized from itaconic anhydride ( 1 ) and cyclopentadiene via a Diels‐Alder reaction, nitric acid oxidation, and the subsequent dehydration with acetic anhydride. The structure of DAn was determined by NMR spectra and single crystal X‐ray diffraction. A series of soluble polyimides ( PI s) having a spiro alicyclic unit in the main chain were prepared by the reactions of DAn with several diamines through a general two‐step polymerization method. Polymerization temperature affected inherent viscosities of poly(amic acid)s. Chemically imidized PI s had the inherent viscosities in the range of 0.10–0.49 dL/g. Due to the unsymmetric spiro alicyclic structure, the PI s showed excellent solubility in many organic solvents. Glass transition temperatures of PI s ranged from 215 to 279°C and some of them showed no glass transition temperature. The 10% weight loss temperatures under nitrogen were in a range of 355–430°C. Films of PI s obtained by the thermal imidization were wholly transparent and colorless.     

Preparation of polyamides having 1,2,4-triazine rings in the main chain

Polyamides having 1,2,4-triazine rings in the main chain ( 6 and 7 ) were prepared from 3-substituted 4,4′-(1,2,4-triazine-5,6-diyl)dibenzoic acids ( 5 ) and aromatic diamines. The thermal stability and the solubility of polyamides 6 and 7 were compared with those of structurally identical polyamides (polymers 3 and 4 ) obtained by polymer homologous reaction of polyamides having α-diketone moieties with amidrazones. The effects of introduction of 1,2,4-triazine-5,6-diyl unit in the main chain on the thermal stability and solubility of the polymers are discussed.     

Synthesis and properties of chlorinated polyimides

A series of diamines with various chlorine content was synthesized. Using these novel diamines, a series of new chlorinated polyimides was prepared by reacting them with 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride (6FDA). The purpose was no investigate the effect of the chlorine content on the properties of polyimides, such as thermal and optical properties. The in‐plane refractive (n_TE) indices of polymer films increase with increasing order of in‐plane orientation in these polyimides. The out‐of‐plane refractive (n_TM) indices increase with chlorine content.     

Synthesis and characterization of new siloxane-modified addition polyimides

A new series of polyimides was synthesized by addition polymerization of 4,4′-(bismaleimido)-diphenylmethane, 1,4-piperazine and an amino-terminated polydimethylsiloxane. The synthesis was carried out in m-cresol solution following a two-step procedure. Copolymers containing 15 and 20 wt.-% of the polydimethylsiloxane elastomer were prepared, together with the unmodified base copolymer. Infrared spectroscopy, ¹³C and ¹H NMR, thermal and thermogravimetric analyses were used to characterize the copolymers. The DSC curves of all the samples showed an exotherm in the temperature range 230–280°C, attributable to curing and addition reactions involving the chain-end groups. Different glass transition temperatures (T_g) were observed, depending on the elastomer content. Thermogravimetric analysis indicated that no significant changes occur in the thermal stability of rubber-modified copolymers.     

Assessment of cyclobutane pyrimidine dimers by digital photography in human skin

UV-mediated DNA damage and repair are important mechanisms in research on UV-induced carcinogenesis. UV-induced DNA-damage and repair can be determined by immunohistochemical staining of photoproduct positive nuclei of keratinocytes in the epidermis. We developed a new method of analysing and quantifying thymine dimer (TT-CPD) positive cells in the epidermis. Normal skin of healthy controls was exposed to UVB ex vivo and in vivo. Skin samples were immunohistochemically stained for TT-CPDs. Digital images of the epidermis were quantified for TT-CPDs both visually and digitally. There was a UVB-dose dependent induction of TT-CPDs present in the ex vivo UVB-irradiated skin samples. The linear measurement range of the digital quantification was increased compared to the manual counting. The average 24-hour repair rate of the initiated TT-CPDs elicited by the UVB irradiation at T=0 of the 8 HCs showed a 34% decrease of TT-CPD photoproducts by the manual counting method and a 51% decrease determined by digital counting. The digital quantification method improves immunohistochemical quantification of DNA photo damage. It is more sensitive in measuring the extent of DNA-damage per nucleus.     

Synthesis and properties of aromatic polyimides derived from 2,7-triptycenediamine

Novel aromatic polyimides were synthesized from 9,10-dihydro-9,10-o-benzenoanthracene-1,5-diamine (2,7-triptycenediamine) and aromatic tetracarboxylic dianhydrides. The polymerization was carried out in a two-step procedure including ring-opening poly-addition giving polyamic acids, followed by thermal cyclodehydration. The polyamic acids have high inherent viscosities (0.97–1.95 dL/g in 1-methyl-2-pyrrolidone). The polyimides show high glass transition temperatures (392–409°C), high decomposition temperatures at 5% weight loss (516–566°C), and high weight residues (64–69% at 800°C). All polyimides are amorphous. The polyimide from the diamine with 3,3′,4,4′-diphenylsulfonetetracarboxylic dianhydride (4,4′-sulfonyldiphthalic anhydride) is soluble in pyridine, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide and conc. sulfuric acid at 60°C, and shows high thermal stability. The introduction of 2,7-triptycenediyl structure into the polyimide backbone has the effect of improving the solubility and maintaining the high thermal stability.     

Synthesis and nonlinear optical properties of high glass transition polyimides

Nonlinear optical (NLO) polymers with glass transition temperatures (T_g) as high as 275°C were prepared by covalent bonding of a chromophore to the backbone of hydroxyl polyimides via a Mitsunobu reaction. NLO side-chain polyimides with different polymer backbones and different chromophores were prepared and characterized by second-harmonic generation. Poled films of the polymers have an excellent nonlinear optical response that is stable at elevated temperatures.     

Ring-opening polymerization of cyclobutane adducts of tetracyanoethylene and vinyl ethers with quaternary ammonium halides

Ring-opening polymerizations of cyclobutane adducts of tetracyanoethylene (TCNE) and vinyl ethers (VE) with quaternary ammonium halides are described. The polymerization of the cyclobutane adduct 5a of TCNE and ethyl vinyl ether (EVE) was carried out with 10 mol-% of tetrabutylammonium iodide (TBAI) in N,N-dimethylacetamide (DMAc) at ambient temperature to afford the alternating copolymer of TCNE and EVE with high molecular weight in good yield without contamination by TBAI. Under the optimum conditions, the cyclobutane adducts of TCNE and a variety of VEs such as butyl vinyl ether, isobutyl vinyl ether, 2,3-dihydrofuran, and 3,4-dihydro-2H-pyran were polymerized to yield similar polymers. On the basis of the fact that the polymer molecular weight increased rapidly at the initial stage and slowly even after the consumption of all monomers, we propose that the iodide ion of TBAI initiates the anionic chain polymerization of the cyclobutane adduct to afford an iodide-substituted macroanion 6 , which is subjected to intermolecular nucleophilic substitution with each other in a step reaction manner. This intermolecular reaction of 6 was further confirmed by a model reaction of cyclobutane with chloromethyl methyl ether in the presence of chloride ion.     

Effect of structural variations on the thermo-oxidative stability of aromatic polyimides

Polyimides were synthesised from a number of diamines and dianhydrides and their stability determined by thermogravimetric analysis at 400°C in air. Wherever possible high molecular weight films obtained by thermal condensation of the polyamic acid intermediates were studied. If this was not possible, films obtained from acetic acid anhydride ciclised polymers or thermally cured powders were used. A well defiend order of stability was observed for the polyimides prepared from pyromellitic dianhydride and a variety of diamines. The simplest and most symmetrical structures had the greatest thermal stability. Lowest stabilities were observed when linking groups were electronegative in nature.     

Stereocontrol mechanism of an organozinc complex having chair-type structure in the polymerization of tert-butylethylene oxide; comparison with propylene oxide

A ring-opening polymerization of racemic tert-butylethylene oxide (t-BEO) was carried out with a well-defined organozinc complex, [CH₃OCH₂CH(CH₃)OZnOCH(CH₃)CH₂OCH₃]₂·[C₂H₅ZnOCH(CH₃)CH₂OCH₃]₂ ([Zn-MP]_2,2), as initiator. The ¹³C NMR analysis showed that the main chain of poly(t-BEO) is isotactic although the initiation reaction between t-BEO and [Zn-MP]_2,2 is much less enantioselective compared with the very high selectivity in the propagation stage. In the R,S-copolymerization reaction of t-BEO (R/S = 64/36), no change in the optical purity of the residual monomer was observed at any extent of conversion. It was concluded from these results that the enantioselection in the propagation stage at any particular site is perfectly governed by the chirality of the first t-BEO molecule that entered and reacted at the site of [Zn-MP]_2,2. The mechanism of the stereocontrol processes for the [Zn-MP]_2,2 initiated polymerization of t-BEO is discussed in comparison with that for the polymerization of propylene oxide.     

NMR spectra of polyimides: Interpretation and local chain motion study

Three kinds of high-performance polyimides 1 (poly(ketone-imide) PKI), 2 (poly(ether-imide) PEI) and 3 (poly(oxy-imide) POI) were studied using nuclear magnetic resonance (NMR). The NMR spectra of the polyimides were assigned according to the comprehensive consideration of the substitution effect of different substituting groups, viz. distortionless enhancement by polarization transfer (DEPT), no nuclear Overhauser effect (NNE), analysis of relaxation time, and two-dimensional correlated spectroscopy (COSY) techniques. The structural units of these three polyimides were determined. Carbon-13 and proton relaxation times for PEI and PKI were interpreted in terms of segmental motion characterized by the sharp cutoff model of Jones and Stockmayer (JS model) and anisotropic group rotation such as phenyl group rotation and methyl group rotation. Correlation times for the main-chain motion are in the tens of picosecond range which indicates the high flexibility of polyimide chains. Correlation times for phenyl group and methyl group rotations are more than 1 order of magnitude lower and approximately 1 order of magnitude higher than that of the main chain, respectively.     

Fabrication of free-standing albumin-nanosheets having heterosurfaces

Sheet-shaped carriers, having both obverse and reverse surfaces and thus a large contact area for targeting a site, have several advantages over spherical-shaped carriers, which have an extremely small contact area for targeting sites. Here, we proposed a novel method to prepare a free-standing ultrathin and biocompatible nanosheet having heterosurfaces, by a combination of four processes: (1) specific adsorption of recombinant human serum albumin (rHSA) molecules onto a patterned octadecyltrimethoxysilane self-assembled monolayer region (ODS-SAM), (2) preparation of nanosheets of rHSA molecules bearing thiol groups (SH-rHSA) via two-dimensionally disulfide crosslinking, (3) surface modification of the resulting nanosheet, and (4) preparation of the free-standing nanosheet by detachment from the ODS-SAM. The SH-rHSA molecules at pH 5.0 and a concentration of 1 microg/mL were specifically adsorbed on the patterned ODS-SAM regions by hydrophobic interaction, and were two-dimensionally crosslinked in the presence of copper ion as an oxidant. The rHSA-nanosheets were then simply detached from the ODS-SAM by treatment with surfactant. We succeeded in the preparation of rectangular (10 microm x 30 microm) and ultrathin (4.5 +/- 1.0 nm) rHSA-nanosheets on a patterned ODS-SAM, and could also obtain free-standing rHSA-nanosheets having heterosurfaces by surface modification with fluorescent latex beads. Thus, the rHSA-nanosheets having heterosurfaces could be regarded as a new biomaterial for drug carriers, hemostatic reagents, wound dressing for burn injury, and so forth.     

Synthesis and properties of polyimides containing 2,2′-bipyridine derivatives

A series of polyimides containing 2,2′-bipyridine, 7 , were synthesized by reaction of 4,4′-diamino-2,2′-bipyridine ( 4 ) with various aromatic dianhydrides, followed by imidization upon heating. These polyimides are fairly thermostable, and 5% weight loss occurs in the range of 484°C-580°C. The glass transition temperatures are between 276°C and 313°C. Their poly(amic acids) 6 can be partially quaternized using 1,2-dibromoethane and then easily imidized upon heating. The temperature of quaternized polyimides at which 5% weight loss is observed is around 300°C, the glass transition temperatures range from 202–239°C. These quaternized polyimides can also develop color under UV irradiation in a poly(N-vinyl-2-pyrrolidone) (PVP) matrix with maximum absorption at 800 nm. The bipyridine-based poly(amic acids) 6 can trap various metal ions from solution and then can be imidized by heating. The XPS data indicate the formation of a 1:1 (bipyridine: metal molar ratio) complex and a 2:1 complex. The temperature at which for the polyimide-metal complexes 5% weight loss is observed is around 300°C. Both the poly(amic acid)-metal complex and the polyimide-metal complex catalyze the condensation of benzaldehyde with acetophenone, with yields of chalcone of ca. 6.7–31.7%. The order of catalytic activity for different metal ions is Zn(II) > Co(II) > Cu(II).     

The consequences of not having eosinophils

Several lines of evidence suggest that deficiency of eosinophils is not associated with any characteristic abnormality. Patients lacking eosinophils, in the setting of immunodeficiency or as a consequence of IgG‐mediated eosinophil precursor destruction, do not display any distinguishing abnormalities related to eosinophil reduction. The observation that eosinophil‐deficient mice do not display any distinctive syndrome or failure of their health is evidence that, under ordinary laboratory conditions, the eosinophil does not play a critical role in the well‐being of mammals. Observations that monoclonal antibodies to interleukin‐5 (IL‐5) are well tolerated appear unsurprising in light of these findings. For example, patients with the hypereosinophilic syndrome have received mepolizumab, an anti‐IL‐5 monoclonal antibody, for as long as 6 years and have not developed any characteristic set of adverse events. Safety data for reslizumab, another anti‐IL‐5 monoclonal antibody, and benralizumab, a monoclonal antibody to the IL‐5 receptor α ‐ chain, are comparatively limited, especially for benralizumab, although reports of administration of these antibodies to humans suggest that they are well tolerated. Thus, data to the present suggest that reduction of eosinophils appears to have no characteristic ill effects on normal health, and monoclonal antibodies that deplete eosinophils have the potential to be widely employed in the treatment of eosinophil‐associated diseases.     

LC-polyimides, 32. Characterization of the Mitsui-Toatsu LC-polyimide and related polyimides

Two polyimides were prepared from 1,3-bis[4′-(4″-aminophenoxy)cumyl]benzene and 1,2:4,5-benzenetetracarboxylic dianhydride (PMDA) or 1,8:4,5-naphthalenetetracarboxylic dianhydride. A poly(amide-imide) was prepared from the same diamine and trimellitic anhydride. Furthermore, two polyimides were prepared from 1,4-bis-[4′-(4″-aminophenoxy)cumyl]benzene or a mixture of the 1,3- and 1,4-diamines. Moreover, one polyimide was synthesized from PMDA and 1,3-(4-aminocumyl)benzene. All polyimides were characterized by elemental analyses, optical microscopy, DSC and various X-ray measurements. Only the polyimide of PMDA and the 1,3-amine proved to be thermotropic. SAXS and WAXS measurements between 25 and 350°C, along with a fiber pattern suggest that this LC-polyimide forms a smectic-A phase in the melt and a disordered smectic-B phase in the solid state. Also most other polyimides formed a disordered smectic-B or a smectic-A glass in the solid state. However, the polyimide derived from 1,3-(4-aminocumyl)benzene crystallized in the form of a smectic-H phase with tilted mesogens. All results together underline the high potential of polyimides of form layer structures.     

Chromatographical investigation and mass spectrometry of cyclic polyimides by matrix-assisted laser desorption

The Diels-Alder addition polymerization of bispyrone 1 with 2 mol bismaleimide 2 was shown to lead to cyclic polyimides 3 (64%, M̄_n = 15 000 g/mol) and to cyclic oligomers (36%) applying by gel-permeation chromatography analysis (GPC) and by means of matrix-assisted laser desorption/ionisation technique (MALDI).     

Genetic and phylogenetic characterization of the type II cyclobutane pyrimidine dimer photolyases encoded by Leporipoxviruses

Shope fibroma virus and myxoma virus encode proteins predicted to be Type II photolyases. These are enzymes that catalyze light-dependent repair of cyclobutane pyrimidine dimers (CPDs). When the Shope fibroma virus S127L gene was expressed in an Escherichia coli strain lacking functional CPD repair pathways, the expressed gene protected the bacteria from 70-75% of the ultraviolet (UV) light-induced cytotoxic DNA damage. This proportion suggests that Leporipoxvirus photolyases can only repair CPDs, which typically comprise approximately 70% of the damage caused by short wavelength UV light. To test whether these enzymes can protect virus genomes from UV, we exposed virus suspensions to UV-C light followed by graded exposure to filtered visible light. Viruses encoding a deletion of the putative photolyase gene were unable to photoreactivate UV damage while this treatment again eliminated 70-90% of the lethal photoproducts in wild-type viruses. Western blotting detected photolyase protein in extracts prepared from purified virions and it can be deduced that the poxvirion interior must be fluid enough to permit diffusion of this approximately 50-kDa DNA-binding protein to the sites where it catalyzes photoreactivation. Photolyase promoters are difficult to categorize using bioinformatics methods, as they do not obviously resemble any of the known poxvirus promoter motifs. By fusing the SFV promoter to DNA encoding a luciferase open reading frame, the photolyase promoter was found to exhibit very weak late promoter activity. These data show that the genomes of Leporipoxviruses, similar to that of fowlpox virus, encode catalytically active photolyases. Phylogenetic studies also confirmed the monophyletic origin of poxviruses and suggest an ancient origin for these genes and perhaps poxviruses.