Ester Units Research Articles

5,10,10,15,20,20-Hexamethylcalix[4]pyrrole 5,15-diethyl diester

In the title compound, C32H40N4O4, the pyrrole rings and ester groups adopt a 1,3-alternate conformation in which the alternating pyrrole and ester units are in opposite directions. The structure displays N—H⋯O hydrogen bonding and exhibits disorder [site occupancies of 0.81(2) and 0.71(2)] in the peripheral ethyl groups.

Ethyl 6-chloro-2-methyl-4-phenylquinoline-3-carboxylate

In the title compound, C19H16ClNO2, the quinoline ring system is planar (r.m.s. deviation = 0.008 Å). The phenyl group and the –CO2 fragment of the ester unit form dihedral angles of 60.0 (1) and 60.5 (1)°, respectively, with the quinoline ring system.

Photoreactive molecular layers containing aryl ester units: Preparation, UV patterning and post-exposure modification

The photolithographic modification of thin functional silane layers provides a versatile and powerful means of fabricating functionalized patterned surfaces which can be applied for tuning inorganic surface properties and for modern immobilisation techniques. In this contribution we present the synthesis of a new functional trichloro organosilane bearing photoreactive aryl ester groups and its application in thin silane layers on silicon oxide surfaces. Whereas the trichlorosilyl group acts as anchoring unit to the inorganic surface, the aryl ester group undergoes the photo-Fries rearrangement to yield hydroxyketones upon irradiation with UV-light of 254 nm which leads to a change in chemical reactivity of the surface. By a subsequent reaction with perfluorobutyryl chloride, the photogenerated hydroxy groups yield the corresponding perfluorinated ester compound, which allows further tuning of surface properties. The layer formation as well as the photoreaction and post-modification reaction was monitored by FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). The thickness of the obtained thin layers was determined by X-ray reflectivity (XRR). Photopatterned surfaces were produced using a contact mask during illumination followed by the post-modification reaction. Friction force microscopy (FFM) revealed the contrast between modified and unmodified regions of the patterned samples.

Degradation of polyesteramides during composting under standard and isothermal conditions

Polyesteramides based on epsilon-caprolactam and epsilon-caprolactone differing in the content of ester-amide structural units were subjected to biodegradation - composting in a big compost pile under controlled conditions (controlled composting) and in small composters at a steady temperature of 60 degrees C (isothermal composting). Both types of composting resulted in degradation of the polyesteramides depending on copolymer composition, isothermal composting being more robust. The contribution of abiotic hydrolysis to the degradation of polyesteramides was studied at 60 degrees C in buffer solutions with pH 5.4, 7.4 and 8.4. The prevailing effect of abiotic hydrolysis over biological one was shown at 60 degrees C. Ester bonds in polyestramide chains were preferentially cleaved; therefore, the scope of degradation increased with the content of ester units in the copolymer.

Copolymerization of norbornene and 5‐norbornene‐2‐yl acetate using novel bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3 catalytic system

AbstractVinyl‐type copolymerization of norbornene (NBE) and 5‐NBE‐2‐yl‐acetate (NBE‐OCOMe) in toluene were investigated using a novel homogeneous catalyst system based on bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3. The copolymerization behavior as well as the copolymerization conditions, such as the levels of B(C6F5)3 and AlEt3, temperature, and monomer feed ratios, which influence on the copolymerization were examined. Without combination of AlEt3, the catalytic bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3 exhibited very high catalyst activity for polymerization of NBE. Combination of AlEt3 in catalyst system resulted in low conversion for polymerization of NBE. For copolymerization of NBE and NBE‐OCOMe, involvement of AlEt3 in catalyst is necessary. Slight addition of NBE‐OCOMe in copolymerization of NBE and NBE‐OCOMe gives rise to significant increase of catalyst activity for catalytic system bis(β‐ketonaphthylamino)Ni(II)/B(C6F5)3/AlEt3. Nevertheless, excess increase of the NBE‐OCOMe content in the comonomer feed ratios results in decrease of conversion as well as activity of catalyst. The achieved copolymers were confirmed to be vinyl‐addition copolymers through the analysis of FTIR, 1H NMR, and 13C NMR spectra. 13C NMR studies further revealed the composition of the copolymer and the incorporation rate was 7.6–54.1 mol % ester units at a content of 30–90 mol % of the NBE‐OCOMe in the monomer feeds ratios. TGA analysis results showed that the copolymer exhibited good thermal stability (Td > 410 °C) and failed to observe the glass transitions temperature over 300 °C. The copolymers are confirmed to be noncrystalline by WAXD analysis results and show good solubility in common organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3990–4000, 2009

Synthesis of Photoacid Generator-Containing Patternable Diblock Copolymers by Reversible Addition−Fragmentation Transfer Polymerization

Novel well-defined, patternable diblock copolymers containing photoacid-generating sulfonium and acid-sensitive ester units in one of the blocks were synthesized by reversible addition−fragmentation transfer polymerization, and their self-assembling as well as lithographic properties were investigated.

Anionic alternating copolymerization behavior of bifunctional six‐membered lactone and glycidyl phenyl ether

AbstractA copolymerization of 10‐methyl‐2H,8H‐benzo‐[1,2‐b:5,4‐b′]bipyran‐2,8‐dione (1) and glycidyl phenyl ether (GPE) was studied. 1 was a bislactone designed as a bifunctional analogue of 3,4‐dihydrocoumarin (DHCM), of which anionic 1:1 alternating copolymerization with GPE has been reported by us, previously. This alternating nature was inherited by the present copolymerization of 1 and GPE, leading to an intriguing copolymerization behavior in contrast to the ordinary statistical copolymerizations of monofunctional monomers and bifunctional monomers usually controlled by the proportional dependence of the crosslinking density on the monomer feed ratio: (1) When the feed ratio [GPE]0/[1]0 was 1, the two monomers underwent the 1:1 alternating copolymerization. In this case, 1 behaved as a monofunctional monomer, that is, only one of the two lactones in 1 participated in the copolymerization allowing the other lactone moiety to be introduced into the side chain almost quantitatively. (2) Increasing the feed ratio [GPE]0/[1]0 to larger than 4 allowed almost all of the lactone moieties to participate in the copolymerization system to give the corresponding networked polymers efficiently. The compositions of the copolymers [GPE unit]/[1‐derived acyclic ester unit] were always biased to smaller values than the feed ratios [GPE]0/[lactone moiety in 1]0 by the intrinsic 1:1 alternating nature of the copolymerization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3662–3668, 2009

Diethyl 2-[(5-methoxy-2-methyl-1-phenylsulfonyl-1H-indol-3-yl)methylene]malonate

In the title compound, C24H25NO7S, the sulfonyl-bound phenyl ring is approximately perpendicular to the indole ring system [dihedral angle = 87.72 (5)°]. The methyl group of one of the ester units is disordered over two positions with occupancies of 0.527 (13) and 0.473 (13). An intra­molecular C—H⋯O hydrogen bond is observed. In the crystal structure, mol­ecules are linked into a ribbon structure running along the c axis by inter­molecular C—H⋯O hydrogen bonds and C—H⋯π inter­actions involving the pyrrole ring.

Methyl 2-(N-methoxycarbonylmethyl-N-methylsulfamoyl)benzoate

In the title compound, C12H15NO6S, the aromatic ring is oriented at dihedral angles of 64.76 (11) and 56.42 (13)° with respect to the planar methyl ester unit and the SO2 group, respectively. The dihedral angle between the SO2 group and the planar methoxy­carbonyl­methyl group is 50.42 (14)°. Intra­molecular C—H⋯O hydrogen bonding results in the formation of an eight-membered ring. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules.

Synthesis of Degradable Materials Based on Caprolactone and Vinyl Acetate Units Using Radical Chemistry

Present studies are carried out with an aim to make degradable materials based on caprolactone and vinyl acetate units using radical chemistry. Radical ring-opening copolymerization of 2-methylene-l,3-dioxepane (MDO) with vinyl acetate in presence of AIBN initiator at 70 °C was carried out to achieve the aim. The copolymerization introduced degradable PCL repeat units onto the C-C backbone of poly(vinyl acetate). Microstructure analysis of the copolymers is done using different ID and 2D NMR techniques. Complete ring-opening polymerization of MDO to give ester units was observed during copolymerizations. Reactivity ratios were found out by Kelen Tudos method and were rVAc = 1.53 and rMDO = 0.47 leading to statistical introduction of ester linkages onto the polymer backbone. The materials showed varied glass transition temperatures (from 37 to −44°C) depending upon the amount of ester linkages and very high elongations. The hydrolysis products were also tested for cytotoxicity studies in L929 cells and compared with that of known and accepted standard materials like poly(ethyleneimine). The hydrolysed products were non toxic and showed a cell viability > 95%. Keeping in view the combined properties like degradability, non-toxicity and low glass transition temperatures, the resulting materials could therefore be proposed for different applications like degradable gums, coatings etc.

Refractive index modulation in polymers bearing photoreactive phenyl and naphthyl ester units using different UV wavelengths

Tuning and patterning of the refractive index in polymeric films is of importance for modern optical applications such as wave guiding and optical data storage. In this contribution, we report on the synthesis of new photoreactive polymers bearing aryl esters which undergo the photo-Fries rearrangement to give aromatic hydroxyketones. Poly(norbornene)-based polymers bearing naphthyl ester groups (poly-2) and copolymers bearing both phenyl and naphthyl ester groups (poly(1-co-2)) were prepared by ring opening metathesis polymerization (ROMP). The photochemistry of these polymers under irradiation with UV light of either 254 nm or 313 nm was investigated. The photoreaction causes an increase of the refractive index in poly-2 between Δn589 = +0.022 and +0.048 depending on the irradiation wavelength. The copolymer poly(1-co-2) offers the possibilities of selectively exciting either the naphthyl ester with UV light of 313 nm causing an increase in the refractive index of Δn589 = 0.010, or both the naphthyl and phenyl chromophores with UV light of 254 nm (Δn589 = 0.036). When thin films of poly(1-co-2) already irradiated with 313 nm light are subjected to a second illumination step with 254 nm light, a significant decrease of the refractive index (Δn589 = −0.043) is observed. The reason for this behaviour seems to arise from the formation of different photoproducts depending on the irradiation sequence. Thus the final refractive index can be adjusted to values between n589 = 1.564 to n589 = 1.633. The two step illumination procedure provides the possibility of erasing and even inverting the index contrast generated during the first illumination step.

Towards a Biocompatible, Biodegradable Copolymer Incorporating Electroactive Oligothiophene Units.

As part of an ongoing effort to develop biocompatible, biodegradable conducting polymers, we report here the synthesis and characterization of a novel copolymer, 5,5"'bishydroxymethyl-3,3"'-dimethyl-2,2':5',2":5",2"'-quaterthiophene-co-adipic acid polyester (QAPE). This system was designed so as to incorporate alternating electroactive quaterthiophene units and biodegradable ester units into one macromolecular framework, while allowing for facile preparation of the polymer via a polycondensation reaction. In agreement with the design expectations, the ester groups were found to be incorporated into the polymer between the quaterthiophene subunits, as inferred from standard chemical and spectroscopic analyses. QAPE exhibited redox activity as detected by cyclic voltammetry and a new red-shifted absorption peak upon doping, providing support for the notion that the quaterthiophene units maintain electroactivity after incorporation into the QAPE polymer framework. The degradation, likely through surface erosion, of this polymer in the presence of cholesterol esterase was confirmed by the detection of a fluorescence signal at wavelengths corresponding to the quaterthiophene subunit and comparisons to appropriate controls. In vitro cytocompatability studies, carried out over 48 h, indicate that the QAPE polymer is nontoxic to Schwann cells.

Synthesis and properties of some polyaminobis maleimides thermal and mechanical characterization

AbstractA series of bismaleimide monomers with various structures were used to prepare poly(aminobismaleimide)s in an attempt to achieve polymers with improved mechanical and thermal properties. Structurally different bismaleimides with ester units and having chlorine substituent at the aromatic ring or hexafluoroisopropylidene(isoprpylidene) group between benzene rings were synthesized by reaction between 3(4)-maleimidobenzoylchloride with various bisphenols. The monomers and polymers were characterized by infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectrometry. Polymers based on these bismaleimides were prepared by Michael addition of diamines to bismaleimides. These polymers exhibited good solubility in N-methylpirrolidone and formed flexible films with good stress-strain properties. The mechanical behaviour of these polymers was investigated by stress-strain measurements on films at room temperature. The influence of the structure of these polymers on their mechanical properties was comparatively studied.

Cobalt-Catalyzed Carbonylative Polymerization of Azetidines

We provide a full account on our study of the cobalt-catalyzed carbonylative polymerization of N-alkylazetidines involving three representative monomers. The individual N-alkylazetidine monomers display different characteristics in the polymerization, allowing the incorporation of amine and ester units into the amide-based polymers. We will first present the synthesis and characterization of poly(amide-co-amine) with a gradient amine distribution. Then, we will describe how to control the ester distribution in poly(amide-co-ester)s. Poly(amide-co-ester)s containing multiple segments, within which the ester units distribute in a gradient fashion, will be compared with multiblock poly(amide-co-ester)s. Finally, we report our discovery of a novel chain transfer pathway via N-benzyl abstraction.

{5,5′-Bis(methoxycarbonylmethoxy)-2,2′-[ethane-1,2-diylbis(nitrilomethylidyne)]diphenolato}copper(II)

The title compound, [Cu(C22H22N2O8)], is a tetra­dentate Schiff base complex. The CuII ion has a nearly square-planar geometry, being coordinated by two N atoms and two O atoms. The two chemically equivalent halves of the mol­ecule are crystallographically independent. One of the carboxylic acid methyl ester units is located in the main plane of the mol­ecule and the other is rotated by 65.3 (5)° with respect to this unit. In the crystal structure, there are π–π stacking inter­actions between adjacent six-membered chelate rings, with centroid-to-centroid distances of 3.602 (2) Å.

Synthesis and Characterization of New Biomedical Polymers: Serine- and Threonine-Containing Polyphosphazenes and Poly(l-lactic acid) Grafted Copolymers

Polyphosphazenes that contain serine and threonine side groups have been synthesized by the macromolecular substitution technique, and their structure and properties were determined. Serine and threonine have two different sites for covalent linkage to the polyphosphazene backbone. For one series of polymers, serine ethyl ester and threonine ethyl ester units were linked to the polyphosphazene skeleton via the N-terminus. The free hydroxyl groups on each side group were then used to graft poly(l-lactide). Graft densities of 1:0.5, 1:2, and 1:4 grafts per repeat unit were controlled through the stoichiometric ratios of sodium naphthalenide to polyphosphazene side groups during the synthetic procedures. For the second series of macromolecules, the hydroxyl function of serine or threonine was used as the site for covalent attachment to the polyphosphazene backbone, a process that required protection of both the N- and C-termini. Secondary reactions to remove the protective groups then yielded side units with free amino and carboxylic acid functions. These polymers (with serine or threonine groups linked via the hydroxyl function) are water-soluble over a broad pH range but have the ability to form ionic cross-links in the presence of calcium ions.

Biodegradable copolyester/starch blends - preparation, mechanical properties, wettability, biodegradation course

A set of blends of an aromatic-aliphatic copolyester containing 35 mol. % of aromatic ester units and plasticized wheat starch has been prepared. The copolyester used in this process was synthesized by polycondensation of the product of solvolysis of polyethyleneterephthalate (PET) from disposed beverage bottles by an aqueous solution of lactic acid. The blends copolyester/starch were characterized by their tensile strength and wetting behavior. Biodegradability of the blends was tested by using of mixed culture of microorganisms of digested sludge from wastewater treatment plant under anaerobic thermophilic conditions (55 °C).

Novel hockey‐stick mesogens with the nematic, synclinic and anticlinic smectic C phase sequence

New hockey‐stick mesogens have been synthesised and their mesomorphic properties studied. The molecular structure consists of a laterally substituted central naphthalene unit prolonged by two non‐symmetrical arms, both of which contain ester units of identical orientation. The shorter arm possesses only one and the longer arm three benzene rings. Nematic, synclinic smectic C and anticlinic smectic C phases were identified and their physical properties studied. No banana‐type ordering producing dipolar phases has been found.

Ethyl 2-[(N-methoxy-N-methylcarbamoyl)methyl]-1-(phenylsulfonyl)-1H-indole-3-carboxylate

In the title compound, C21H22N2O6S, the phenyl ring forms a dihedral angle of 83.17 (7)° with the indole ring system. The methyl group of the ester unit is disordered over two positions with site occupancies of 0.635 (6) and 0.365 (6). In the crystal structure, weak intra­molecular C—H⋯O inter­actions and inter­molecular C—H⋯O, C—H⋯N and C—H⋯π inter­actions are observed.

Duocarmycin-based prodrugs for cancer prodrug monotherapy

The synthesis and biological evaluation of novel prodrugs based on the cytotoxic antibiotic duocarmycin SA ( 1) for a selective treatment of cancer using a prodrug monotherapy (PMT) are described. Transformation of the phenol 8 with the glucuronic acid benzyl ester trichloroacetimidate 9b followed by reaction with DMAI·HCl ( 10) gives the glucuronide 11b, which is deprotected to afford the desired prodrug 4a containing a glucuronic acid moiety. In addition, the prodrug 4b with a glucuronic methyl ester unit is prepared. The cytotoxicity of the glucuronides is determined using a HTCFA-assay with IC 50 values of 610 nM for 4a and 3300 nM for 4b. In the presence of β-glucuronidase, 4a expresses an IC 50 value of 0.9 nM and 4b of 2.1 nM resulting in QIC 50 values of about 700 for 4a and 1600 for 4b.