Synthesis of a novel N‐selective ester functionalized chitin derivative and water‐soluble carboxyethylchitin

A novel chitin derivative having a pendant ester function, 2‐N‐(2‐ethoxycarbonylethyl)chitin ( 2 ), was synthesized by a Michael‐type nucleophilic addition of an amino group of partially deacetylated chitin ( 1 ) to ethyl acrylate in phosphate buffer/methanol (5 : 3, v/v) at 40°C. N‐Selective monosubstitution occurred exclusively in the polymer reaction, which was supported by a reaction of methyl 2‐amino‐2‐deoxy‐D ‐glucopyranoside with ethyl acrylate to afford methyl 2‐N‐(2‐ethoxycarbonylethyl)‐2‐amino‐2‐deoxy‐D ‐glucopyranoside. The degrees of substitution (DSs) of 2 were determined by ¹H NMR spectroscopy. T₁ analysis of 2 was carried out in order to clarify differences of signal intensities of the pendant ester protons and the pyranose ring protons. The result of the T₁ measurement suggested a relatively restricted molecular motion of the chitin backbone in comparison with the flexible pendant ethyl ester groups. Furthermore, 2‐N‐(2‐carboxyethyl)chitin sodium salt ( 3 ) was synthesized from ethyl acrylate and 1 by the Michael addition followed by hydrolysis in 0.1 N NaOH aq. at 40°C. The DSs of 3 were varied from 0.26 to 0.88, which were almost controlled by the reaction period of the Michael reaction from 6 to 168 h. 3 showed good solubility in water. Viscosity measured on a cone‐plate viscometer for the 1.0 wt.‐% aqueous solution of 3 (DS, 0.26) was 0.074 Pas·sec.     

Functionalized Biocompatible Poly(N‐vinyl‐2‐caprolactam) With pH‐Dependent Lower Critical Solution Temperature Behaviors

Functionalized temperature‐ and pH‐sensitive poly(N‐vinyl‐2‐caprolactam) (PVCL) polymers are prepared by copolymerizing monomers of N‐vinyl‐2‐caprolactam (VCL) and a VCL derivative, 3‐(tert‐butoxycarbonyl)‐N‐vinyl‐2‐caprolactam (TBVCL). Different molar compositions are studied, with the functional monomer at 9 and 14 mol%, respectively, (COOH‐PVCL9 and COOH‐PVCL14). Sharp, complete, and reversible phase transitions of the copolymers with little hysteresis are shown to be pH‐dependent, with cloud points ranging from 35 to 44 °C for COOH‐PVCL9, and 29 to 64 °C for COOH‐PVCL14, upon pH change from 2.0 to 7.4. Cytotoxicity assay demonstrates that the functionalized PVCL copolymers are biocompatible with NIH/3T3 up to 2 mg mL^?1. Such new PVCL‐based water soluble copolymers with tunable properties could be useful in a variety of biomedical applications.     

Hydrogen Bonding Interaction and Miscibilization of Ternary Blends of Poly(2‐vinylpyridine), Poly(N‐vinyl‐2‐pyrrolidone), and 4,4′‐(1,4‐Phenylenediisopropylidene)bisphenol

The interaction energy densities of poly(2‐vinylpyridine) (P2VPy)/4,4′‐(1,4‐phenylenediisopropylidene)bisphenol (PDIPBP) blend and poly(N‐vinyl‐2‐pyrrolidone) (PVP)/PDIPBP blend were determined using melting point depression method. The interaction between PVP and PDIPBP is stronger than that between P2VPy and PDIPBP. Wide‐angle X‐ray diffraction study revealed that PDIPBP crystallizes out from the polymer/PDIPBP blends at high PDIPBP contents. The phase equilibrium calculation supports that the single‐T_g behavior is a result of miscibilization rather than an overlap of two close T_g's of two separated phases. The critical miscibilization content of PDIPBP obtained from spinodal phase boundary calculation is lower than the saturation content, and therefore, there is enough PDIPBP in the amorphous phase to miscibilize P2VPy and PVP. Scanning electron microscopy showed a drastic reduction in domain size in single‐T_g blends.

Ternary phase diagram of P2VPy/PVP/PDIPBP blends. (○) miscible blends; (?) immiscible blends; (— × —) calculated phase boundary (Coordinate in volume fraction).     

Synthesis of New Hydrogels by Copolymerization of Poly(2‐methyl‐2‐oxazoline) Bis(macromonomers) and N‐Vinylpyrrolidone

New non‐ionic hydrogels were synthesized by radical homopolymerization of vinyl end‐functionalized poly(2‐methyl‐2‐oxazoline) bis(macromonomers), or by radical copolymerization of these bis(macromonomers) with N‐vinyl‐2‐pyrrolidone (NVP). The poly(2‐methyl‐2‐oxazoline) bis(macromonomers) were synthesized through “living” cationic ring‐opening polymerization of 2‐methyl‐2‐oxazoline (MeOXA), using, simultaneously, the known “initiating” and “end‐capping” method for synthesis of macromonomers. Chloromethyl styrene was used as initiator and N‐(4‐vinylbenzyl)‐piperazine was used as the terminating agent. Well defined poly(2‐methyl‐2‐oxazoline) bis(macromonomers) were obtained with P_n = 4, 11, and 17. The hydrogel structures were characterized by high‐resolution magic angle spinning NMR technique and their solvent absorption capacity was tested by swelling experiments in different solvents. The bis(macromonomers) were characterized by NMR spectroscopy and gel permeation chromatography.

Schematic of polymerization     

Expression of toll‐like receptors in T lymphocytes stimulated with N‐(3‐oxododecanoyl)‐L‐homoserine lactone from Pseudomonas aeruginosa

The establishment of chronic Pseudomonas aeruginosa infections is correlated with the disturbance of the host immune system. The P. aeruginosa quorum‐sensing molecule N‐3‐(oxododecanoyl)‐L‐homoserine lactone (3‐O‐C12‐HSL) has the potential to modulate the host immune system. The immune system recognizes pathogens via toll‐like receptors (TLRs). We found that 3‐O‐C12‐HSL induced TLR changes in monocytes. However, the role of T cells in P. aeruginosa infection has not been delineated. In order to understand this activity, we examined whether 3‐O‐C12‐HSL has an effect on the immune function and the expression of TLRs in T lymphocytes. Human peripheral blood mononuclear cells (PBMCs) cells were cultured with 0, 1, 10, 50, or 100 μM 3‐O‐C12‐HSL for 12 h. TLR2/TLR4 expression and T‐lymphocyte proliferation were increased in a dose‐dependent manner, and 100 μM 3‐O‐C12‐HSL significantly increased TLR2 expression. Moreover, tumor necrosis factor‐α production of these PBMCs was inhibited. To conclude, 3‐O‐C12‐HSL can induce lymphocyte cell proliferation. These findings provide a new perspective on our understanding of the persistence of the chronic inflammation that accompanies P. aeruginosa infection.     

Synthesis and Properties of New N‐Methylated Aliphatic‐Aromatic Polyamides Derived from N,N′‐Dimethylalkylenediamines and 4,4′‐Biphenyl‐dicarboxylic and 4,4″‐p‐Terphenyldicarboxylic Acids

Two new series of N‐methylated aliphatic‐aromatic polyamides were prepared by interfacial polycondensation of N,N ′‐dimethylalkylenediamines having 6–10 methylene units with 4,4′‐biphenyldicarbonyl and 4,4″‐p‐terphenyldicarbonyl chlorides. All of the N‐methylated polyamides were soluble in chlorinated hydrocarbon solvents, and the solubilities of the biphenyl‐based polyamides were higher than those of the terphenyl‐containing polymers. The biphenyl‐bearing polyamides with an even‐number of methylene units were crystalline and their odd‐numbered neighbors were amorphous, whereas all of the terphenyl‐containing polymers were crystalline. The melting temperatures of the terphenyl‐based polyamides (220–307°C) were higher than those of the biphenyl‐bearing polymers (180–207°C). Among these N‐methylated polyamides, the terphenyl‐containing polyamide having 7 methylene units showed enantiotropic liquid crystallinity.     

Crosslinked polymer gels for boron extraction derived from N‐glucidol‐N‐methyl‐2‐hydroxypropyl methacrylate

Glycidyl methacrylate was reacted in 2‐methyl pyrrolidone solution with N‐methyl‐D ‐glucamine (NMG) to produce N‐D ‐glucidol, N‐methyl‐2‐hydroxy propyl methacrylate (GMHP). The reaction proceeded exclusively via ring opening of the oxirane. The resulting vinyl monomer was a waxy product and soluble in water, ethanol, methanol, DMF, and NMP. Copolymerization of GMHP with N,N′‐tetraallyl piperazinium dichloride by the inverse suspension method (water in oil), using a toluene/chloroform (3 : 1) mixture as continuous phase, led to crosslinked hydrogels in imperfect bead form. Crosslinking was also achieved without using additional crosslinker. Heating of N‐methyl‐D ‐glucamine with 10% excess of glycidyl methacrylate in NMP at 60°C for 4 h, resulting the formation of N‐methyl‐D ‐glucamine carrying two methacrylate groups. These dimethacrylate groups serve as a crosslinking agents. In situ redox polymerization of the mixture in water led to transparent hydrogels. These hydrogels in the swollen state have been demonstrated to be very efficient sorbents for the removal of boron on ppm levels. The boron loaded polymers can be regenerated by simple acid (0.1 M HCl) and base (0.1 M NaOH) treatment.     

Thermal,Mechanical, and Surface Properties of Poly(2‐N‐alkyl‐2‐oxazoline)s

Thermal, mechanical, and surface properties of a library of poly(2‐oxazoline)s are investigated. These polymers are suitable to study structure/property relationships as their cationic ROP and the relative facile monomer synthesis allow for control over the molecular structure. The number of carbon atoms in the linear side‐chain is systematically varied from methyl to nonyl. Relations between chemical structures, thermal transitions, surface energies, and elastic moduli are discussed. It is shown that the mechanical and thermal properties of the polymers depend on the presence of a crystalline phase in the material. The amorphous polymers reveal a decrease in the reduced moduli along with a decrease in their respective glass transition temperature with increasing length of the side‐chain.

     

From Old to New: Polymers from Mono‐α‐Alkylated N‐vinylcaprolactam

N‐vinylcaprolactam (NVCL) is modified via alkylation at the α‐position. The α‐substituents are ethyl (3‐ethyl‐1‐vinylcaprolactam), dodecyl (3‐dodecyl‐1‐vinylcaprolactam), octadecyl (3‐octadecyl‐1‐vinylcaprolactam), 1‐propanol (3‐(3‐hydro­xy‐propyl)‐1‐vinylcaprolactam), and PEG₃ bromide (3‐PEG₃‐bromide‐1‐vinylcaprolactam). These monomers are homo‐ and copolymerized with N‐(4‐methylphenyl)­maleimide by the free radical mechanism. The structures of the obtained polymers are characterized by means of ¹H NMR and IR spectroscopy, gel permeation chromatography (GPC), and by use of differential scanning calorimetry (DSC) (T_g).

     

Influence of β‐Cyclodextrin on the Free‐Radical Copolymerization of N‐(4‐Methylphenyl)maleimide with N‐Vinylpyrrolidone in Water

Randomly methylated β‐cyclodextrin (me‐β‐CD) is used to include the hydrophobic monomer N‐(4‐methylphenyl)maleimide (MPM) ( 1 ) yielding the corresponding water‐soluble host‐guest structure 1a . Free‐radical copolymerization of 1a with N‐vinylpyrrolidone (NVP) ( 2 ) is performed and the reactivity ratios r₁ and r₂ are determined: 0.24 ± 0.03 (r₂) and 1.10 ± 0.05 (r_1a). This indicates a preferred incorporation of complexed maleimide into the copolymer chain. In contrast to that, the copolymerization of the uncomplexed monomers 1 and 2 is carried out using organic solvent (DMF/H₂O) showing reactivity ratios corresponding to nearly alternating copolymerization (r₂ = 0.09 ± 0.02; r₁ = 0.34 ± 0.03).

     

FTIR spectroscopy and strengthening behavior of liquid crystalline oligomers of 2‐alkoxy‐4‐hydroxybenzoic acids and 4‐hydroxybenzoic acid

A series of liquid crystalline oligomers of 4‐hydroxybenzoic acid (HBA) and 2‐alkoxyHBAs were synthesized. The structural and conformational changes of the oligomers were studied by FTIR spectroscopy. The strengthening abilities of the synthesized co‐oligomers were investigated by blending the oligomers with polyamide 11 (PA 11).     

Synthesis and Optical Properties of Poly[2‐{N‐Methyl‐N‐(4‐(4‐ethynylphenylazo)phenyl)amino}ethyl butyrate]

Summary: The high‐molecular‐weight functional polyacetylene that contain a para‐aminoazobenzene chromophore, poly[2‐{N‐Methyl‐N‐(4‐(4‐ethynylphenylazo)phenyl)amino}ethyl butyrate] [poly(EAPAB)], was synthesized in moderate yield and characterized by FT‐IR, ¹H NMR, UV‐vis, TGA, and GPC. The nonlinear optical and optical limiting properties were performed with 8 ns pulse width at 532 nm wavelength. The results show that the introduction of the flexible amino group effectively improved the solubility of polymer [poly(EAPAB)] in common organic solvent, such as CHCl₃, THF, and dioxane, while poly(4‐ethynylazobenzene) [poly(4EAB)] without the flexible amino group shows poor solubility in common organic solvent. Simultaneously, poly(EAPAB) still shows good thermal stability, large third‐order nonlinear optical property, and novel optical limiting property owing to the functionalization of the para‐aminoazobenzene chromophore.

Polymerization of EAPAB by Rh(nbd)Cl₂‐Et₃N to poly(EAPAB).     

Occurrence of diversified N‐acyl homoserine lactone mediated biofilm‐forming bacteria in rice rhizoplane

Quorum sensing (QS)‐mediated biofilm‐forming rhizobacteria are indispensable due to their competitiveness in the crop rhizosphere. In the present work, we have reported on the occurrence of diversified bacterial species capable of producing N‐acyl homoserine lactone (AHL) as the QS signal in the roots of a rice plant grown under field conditions. The AHL‐producing bacteria were directly isolated from the rice root by the biosensor reporter (Chromobacterium violaceum CV026) overlay method and characterized for biofilm production by the microtiter plate method. A total of 48 QS‐positive bacterial isolates were purified from different aged (7, 20, 24, 26, and 36 days) rice seedlings. The in vitro biofilm production and genetic diversity as revealed by BOX‐PCR fingerprinting showed high variability among the isolates. Most of the best biofilm‐forming isolates produced a N‐butyryl dl ‐homoserine lactone (a C4‐AHL type) signal in the medium. The 16S ribosomal RNA (rRNA) gene sequence of these putative elite isolates identified that they were close to Aeromonas hydrophila (QS7‐4; QS36‐2), A. enteropelongenes (QS20‐8), A. veronii (QS36‐3), Enterobacter sp. (QS20‐11), Klebsiella pneumoniae (QS24‐6), Kosakonia cowanii (QS24‐21), Providentia rettigeri (QS24‐2), Sphingomonas aquatilis (QS24‐17), and Pseudomonas sihuiensis (QS24‐20). These strains profusely colonized the rice root upon inoculation and formed biofilms on the surface of the root under gnotobiotic conditions. Developing inoculants from these strains would ensure competitive colonization on the rhizoplane of the crop through their biofilm and thereby improve plant growth and health.     

The advanced glycation end‐product Nϵ‐carboxymethyllysine promotes progression of pancreatic cancer: implications for diabetes‐associated risk and its prevention

Diabetes is an established risk factor for pancreatic cancer (PaC), together with obesity, a Western diet, and tobacco smoking. The common mechanistic link might be the accumulation of advanced glycation end‐products (AGEs), which characterizes all of the above disease conditions and unhealthy habits. Surprisingly, however, the role of AGEs in PaC has not been examined yet, despite the evidence of a tumour‐promoting role of receptor for advanced glycation end‐products (RAGE), the receptor for AGEs. Here, we tested the hypothesis that AGEs promote PaC through RAGE activation. To this end, we investigated the effects of the AGE N^?‐carboxymethyllysine (CML) in human pancreatic ductal adenocarcinoma (PDA) cell lines and in a mouse model of Kras‐driven PaC interbred with a bioluminescent model of proliferation. Tumour growth was monitored in vivo by bioluminescence imaging and confirmed by histology. CML promoted PDA cell growth and RAGE expression, in a concentration‐dependent and time‐dependent manner, and activated downstream tumourigenic signalling pathways. These effects were counteracted by RAGE antagonist peptide (RAP). Exogenous AGE administration to PaC‐prone mice induced RAGE upregulation in pancreatic intraepithelial neoplasias (PanINs) and markedly accelerated progression to invasive PaC. At 11 weeks of age (6 weeks of CML treatment), PaC was observed in eight of 11 (72.7%) CML‐treated versus one of 11 (9.1%) vehicle‐treated [control (Ctr)] mice. RAP delayed PanIN development in Ctr mice but failed to prevent PaC promotion in CML‐treated mice, probably because of competition with soluble RAGE for binding to AGEs and/or compensatory upregulation of the RAGE homologue CD166/ activated leukocyte cell adhesion molecule, which also favoured tumour spread. These findings indicate that AGEs modulate the development and progression of PaC through receptor‐mediated mechanisms, and might be responsible for the additional risk conferred by diabetes and other conditions characterized by increased AGE accumulation. Finally, our data suggest that an AGE reduction strategy, instead of RAGE inhibition, might be suitable for the risk management and prevention of PaC. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Copolymerization of ethylene with 5‐vinyl‐2‐norbornene in the presence of the Ph2C(Flu)(Cp)ZrCl2 /MAO catalyst

Cycloolefin copolymer, poly[(ethylene)‐co‐(5‐vinyl‐2‐norbornene)], was synthetized using the MAO activated ansa‐metallocene Ph₂C(Flu)(Cp)ZrCl₂ as a catalyst. Formation of mostly isolated 5‐vinyl‐2‐norbornene sequences was confirmed by NMR analysis. Comonomer incorporated selectively via cyclic double bond. No selectivity towards the reactivity of the particular isomer of 5‐vinyl‐2‐norbornene (5‐endo : 5‐exo) was observed. The molar mass was found to decrease when the comonomer concentration in product increased. At low comonomer incorporation levels copolymers were insoluble, cross‐linked elastomers. With high comonomer concentration in reaction medium copolymers were amorphous determined by means of DSC and X‐ray diffraction and the vinyl group of the comonomer remained unreacted for further modification.     

Well‐Defined Ruthenium‐Coordinated Block Copolymers of 2‐Vinylpyridine with 2‐(N‐Carbazolyl)ethyl Methacrylate and Their Optical Properties

In order to study the energy‐transfer phenomenon in ruthenium‐coordinated polymers, novel block copolymers from carbazolylethyl methacrylate and 2‐vinylpyridine were prepared by living anionic polymerization; the copolymers possessed varying repeating units and had the desired molecular weight and a narrow‐molecular‐weight distribution. The ruthenium‐coordinated block copolymers were formed by reacting [Ru^II(tpy)(dmbpy)Cl] with the polymers, in which the pyridine units acted as ligands. Photoluminescence and optical absorption measurements of the coordinated block copolymers were carried out to observe the energy transfer in the complexes. The energy transfer from the carbazole blocks to the ruthenium‐coordinated blocks might take place either by an intra‐ and/or an intermolecular energy‐transfer mechanism. From the optical absorption, photoluminescence, and electroluminescence studies, it was observed that the ease of the energy transfer increased with an increasing number of metal‐complex units.

Normalized electroluminescence spectra of the device (ITO/PEDOT/Ru^IIL₂bpolym/TAZ/Alq₃/Ag).     

Photosensitization of N,N‐Dimethylaniline by N,N‐Dimethyl‐4‐nitroaniline as a New Bimolecular Photoinitiation System for Polymerization

Photophysics, photochemical and polymerization activity of N,N‐dimethyl‐4‐nitroaniline (DMNA) alone and in the presence of N,N‐dimethylaniline (DMA) as coinitiator were analyzed to elucidate the influence of the bifunctional character of this compound on the efficiency and mechanism of generating initiating radicals. The presence of electron donor and acceptor groups in the same molecule determines the capability of DMNA to initiate the polymerization with higher efficiency and lower initiator consumption as compared with conventional bifunctional ketones. Detailed studies of the spectroscopy of both reactants were carried out providing experimental evidence of photosensitization of DMA through excitation energy transfer from DMNA. The consumption rate of both reactants reveals that up to 165 molecules of DMA are consumed for each DMNA molecule photoreduced in spite of the low photoreduction quantum yield of DMNA induced by DMA. The photosensitization of DMA, working concurrently to the photoreduction reaction, enhances the polymerization efficiency as compared with other nitroaromatic initiators.     

Hyperbranched Polymers Made from A2‐ and BB′2 ‐Type Monomers, 3. Polyaddition of N‐Methyl‐1,3‐propanediamine to Divinyl Sulfone

The new approach to the synthesis of hyperbranched polymers from commercially available A₂‐ and BB′₂‐ type monomers has been developed further. In this work, hyperbranched poly(sulfone amine)s with multiple amino end groups were prepared by direct polyaddition of N‐methyl‐1,3‐propanediamine (NPA, BB′₂) to divinyl sulfone (DV, A₂). The polymerization mechanism is presented and demonstrated with FT‐IR, HPLC, and MS. During the reaction, the secondary amino groups of NPA react with the vinyl groups of DV within 12 s, generating dimers that can be regarded as new AB′₂‐ type monomers. Further polymerization of the new monomers leads to hyperbranched poly(sulfone amine)s. The influence of the reaction conditions, such as the feed ratio and solvents, on the polymerization has been investigated. When the molar feed ratio of DV to NPA is equal to 1 (A/B/B′ = 2/1/2), no crosslinking is observed in water or organic solvents. When the feed ratio of DV to NPA is equal to 3/2 (A/B/B′ = 3/1/2), no gelation occurs in chloroform or other organic solvents, such as N,N‐dimethylformamide, N,N‐dimethylacetamide, and N‐methyl‐2‐pyrrolidone. Interestingly, when the polymerization was carried out in water with a feed ratio of 3/2, the reaction mixture got turbid within 20–30 min and gelation occurred within 15–20 h.     

Synthesis and Properties of pH‐ and Temperature‐Sensitive Poly[(N‐isopropylacrylamide)‐co‐(2‐methylenebutane‐1,4‐dioic acid)] Hydrogels

Summary: Hydrogels of NIPA and MBDA were synthesized by free‐radical crosslinking copolymerization with different monomer ratios and with two concentrations of the crosslinking agent. The aim of this work was to study the swelling behavior of these gels that are both temperature and pH sensitive. PNIPA hydrogels are typical examples of thermo‐shrinking hydrogels with a LCST, T_C, around 31–34 °C. MBDA is a weakly ionizable monomer which imparts a pH sensitiveness to the copolymer hydrogels. The pH influence on the swelling behavior of the studied hydrogels was analyzed using deionized water and aqueous HCl and NaOH as swelling media. According to the results found in deionized water, the swelling processes of P(NIPA‐MBDA) hydrogels follow second‐order kinetics at 22 and 37 °C. The equilibrium water content, W_∞, and the rate constant, K, increased at greater concentrations of MBDA and decreased as the crosslinking agent concentration increased. As the MBDA content in the hydrogel increased, the collapsing of the hydrogels at higher temperatures than the LCST became of less importance. The degree of swelling of pure PNIPA hydrogels was not influenced by the pH of the swelling medium. However, this influence increased as the MBDA content increased. This was due to the fact that at low pH most of the MBDA units are in the protonated (neutral) form and at high pH in the ionized one.

Swelling isotherms of hydrogels with different copolymer compositions and with 1.5 wt.‐% of BIS at 22 °C in deionized water.