Nonsymmetric Monomer Research Articles

Syntheses of polynorbornadienes by ring-opening metathesis polymerizations of symmetric and non-symmetric 2,3-bis(alkoxycarbonyl)norbornadienes and their conversion to half-ester derivatives.

Libraries of polynorbornadienes were synthesized with good yields with a ruthenium-containing 2nd generation Grubbs catalyst by ring-opening metathesis polymerization (ROMP) of a variety of symmetric and non-symmetric 2,3-bis(alkoxycarbonyl)norbornadiene monomer units prepared from the half-esters obtained efficiently by the selective monohydrolysis reactions of symmetric diesters we reported earlier. Among these polymers, the polynorbornadienes with t-butoxycarbonyl groups derived from non-symmetric monomer units were converted to the half-ester derivatives by deprotection with trifluoroacetic acid, yielding amphiphilic polymers. The hydrogenation reactions of the obtained polymers were carried out to yield polymers having saturated structures in the main chains for improvement of the thermal stabilities. All these polymers were characterized by their molecular weights and thermal properties along with the spectroscopic data. Our selective monohydrolysis reactions have been proven to be a versatile tool for production of relatively homogeneous polymer libraries.

Detecting internally symmetric protein structures

BackgroundMany functional proteins have a symmetric structure. Most of these are multimeric complexes, which are made of non-symmetric monomers arranged in a symmetric manner. However, there are also a large number of proteins that have a symmetric structure in the monomeric state. These internally symmetric proteins are interesting objects from the point of view of their folding, function, and evolution. Most algorithms that detect the internally symmetric proteins depend on finding repeating units of similar structure and do not use the symmetry information.ResultsWe describe a new method, called SymD, for detecting symmetric protein structures. The SymD procedure works by comparing the structure to its own copy after the copy is circularly permuted by all possible number of residues. The procedure is relatively insensitive to symmetry-breaking insertions and deletions and amplifies positive signals from symmetry. It finds 70% to 80% of the TIM barrel fold domains in the ASTRAL 40 domain database and 100% of the beta-propellers as symmetric. More globally, 10% to 15% of the proteins in the ASTRAL 40 domain database may be considered symmetric according to this procedure depending on the precise cutoff value used to measure the degree of perfection of the symmetry. Symmetrical proteins occur in all structural classes and can have a closed, circular structure, a cylindrical barrel-like structure, or an open, helical structure.ConclusionsSymD is a sensitive procedure for detecting internally symmetric protein structures. Using this procedure, we estimate that 10% to 15% of the known protein domains may be considered symmetric. We also report an initial, overall view of the types of symmetries and symmetric folds that occur in the protein domain structure universe.

Synthesis and Characterization of Ordered Poly(urethane−urea)s from p-Isocyanatobenzyl Isocyanate and 4-Aminophenylethyl Alcohol

The ordered (-abcd-) poly(urethane−urea) was prepared by the polyaddition reaction of two nonsymmetric monomers, p-isocyanatobenzyl isocyanate (XabX) (1) with 4-aminophenylethyl alcohol (YcdY) (2) in the presence of dibutyltin dilaurate as a catalyst. The polymerization was conducted in N,N-dimethylformamide (DMF) at 0 °C by mixing both monomers all at once, producing the ordered poly(urethane−urea) with a number-averaged molecular weight of 49 000. Authentic ordered and random poly(urethane−urea)s were prepared to verify the structure of the ordered polymer. The microstructure of polymer obtained was investigated by 1H and 13C NMR spectroscopy, and the expected (-abcd-) ordered structure was confirmed. The constitutional regularity influenced the solubility, crystallinity, and thermal and mechanical properties of polymers. Furthermore, the model reactions were studied in detail to demonstrate the feasibility of polymer formation.

A comparison between state-of-the-art ‘gilch’ and ‘sulphinyl’ synthesised MDMO-PPV/PCBM bulk hetero-junction solar cells

To obtain photovoltaic devices based on electron donating conjugated polymers with a higher efficiency, a major breakthrough was realised by mixing the polymers with a suitable electron acceptor, thereby enhancing the rate for photo-induced charge generation by several orders. State-of-the-art organic bulk hetero-junction photovoltaic cells are based on an interpenetrating donor–acceptor network in the bulk to form efficient nanostructured p–n junctions in the organic materials. Devices made with ‘Gilch’ poly(2-methoxy-5-(3′,7′-dimethyl-octyloxy))- p-phenylene vinylene, (MDMO-PPV), as an electron donor and (6,6)-phenyl-C 61-butyric-acid (PCBM) (a soluble C60 derivative) as an electron acceptor yielded the highest efficiency until now in this class of devices. A power conversion efficiency of approximately η e≥2.5% (electrical power out/incident light power) under AM 1.5 illumination was reported. The ‘gilch’ route is a direct synthetic route. The ‘sulphinyl’ route is a promising, indirect precursor-route towards MDMO-PPV. Due to the non-symmetric monomer, so-called ‘head-to-head’ and ‘tail-to-tail’ additions are excluded to a higher level in comparison to the ‘gilch’ route. This difference between both materials makes them interesting candidates to compare them in the state-of-the-art photovoltaic devices. Preliminary results indicate that the ‘sulphinyl’ MDMO-PPV/PCBM bulk hetero-junction solar cells attain a power conversion efficiency of nearly η e=3% (electrical power out/incident light power), have a higher fill factor, incident photon per converted electron value (IPCE) and short circuit current. It is indicated that the observed solar cell characteristics are related to the defect level of the conjugated polymer used.

Constitutional Isomerism: Synthesis and Characterization of Ordered Polyamides from Isophthalic Acid and N-Phenylethylenediamine by Direct Polymerization

An ordered (head-to-head (H–H) or tail-to-tail (T–T)) polyamide was prepared by direct polycondensation of a symmetric monomer, isophthalic acid (1) with N-phenylethylenediamine (2) as a non-symmetric monomer using the condensing agent diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate. The polycondensation was carried out by slow addition of (1) to (2), and gave polyamide (3d) with an inherent viscosity of 0.29 dl g−1. On the other hand, authentic H–H or T–T ordered polyamide (3a) and H–T ordered polyamide (3b) were obtained by a multi-step route. Random polyamide (3c) was synthesized by mixing isophthaloyl chloride and 2 all at once in N-methyl-2-pyrrolidinone. The microstructure of the polymers was investigated by 1H and 13C NMR spectroscopy. It was found that their spectra were different due to their different constitutions, while polymer 3d obtained by direct polycondensation had the expected H–H or T–T sequence. Furthermore, the model reactions were studied in detail to demonstrate the feasibility of selective amidation and polymer formation.

Synthesis and Characterization of Ordered Polyurethanes from Tolylene 2,4-Diisocyanate and Ethylene Glycol

An ordered polyurethane with a head-to-head or tail-to-tail (H–H or T–T) content of 90% was prepared by polyaddition reaction of a nonsymmetric monomer, tolylene 2,4-diisocyanate (1) with a symmetric monomer, ethylene glycol (2). The polymerization was conducted in toluene in the presence of dibutyltin dilaurate (DBTL) at 0°C by slow addition of a half amount of 2 to 1, followed by removing toluene and then adding the rest of 2 in DMF at once at room temperature in the presence of DBTL. Furthermore, the authentic ordered and random polymers were prepared to verify the structure of the ordered polymer and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced on their thermal properties.

Constitutional Isomerism IV. Synthesis and Characterization of Poly(amide-ester)s from Isophthaloyl Chloride and 4-Aminophenethyl Alcohol

The ordered [head-to-head (H-H) or tail-to-tail (T-T)] poly(amide-ester) was prepared by direct polycondensation of a symmetric monomer, isophthaloyl chloride with 4-aminophenethyl alcohol as a nonsymmetric monomer. The polymerization was conducted in NMP in the presence of triethylamine (TEA) at 0°C by slow addition of isophthaloyl chloride to 4-aminophenethyl alcohol, giving the ordered H-H or T-T poly(amide-ester) with an inherent viscosity of 0.30 dL g−1, measured at a concentration of 0.5 g dL−1 at 30°C in NMP. The authentic H-H or T-T and random poly(amide-ester)s were prepared respectively to varify the structure of ordered polymer. The microstructure of polymers obtained was investigated by 1H and 13C spectroscopy, and it was found that the polymers obtained by direct polycondensation had the expected H-H or T-T ordered structure. The model reactions were studied in detail to demonstrate the feasibility of polymer formation. H-H or T-T ordered polymer was crystalline; On the other hand, the random poly(amide-ester) was amorphous. Furthermore, physical properties of H-H or T-T ordered polymer were compared with poly(amide-ester) obtained from isophthaloyl chloride and 4-(2-aminoethyl)phenol (constitutional isomer of monomer 4-aminophenethyl alcohol).

Synthesis and characterization of ordered poly(amine thioether)s from 1,4-phenylene diacrylate and 4-aminobenzenethiol

An ordered head-to-head (H-H) or tail-to-tail (T-T) poly(amine thioether) was prepared by direct polyaddition of a non-symmetric monomer, 4-aminobenzenethiol (XabX) (1) with a symmetric monomer, 1,4-phenylene diacrylate (2). The reaction was conducted in m-cresol in the presence of a catalytic amount of acetic acid. The authentic ordered H-H or T-T polymer and the random polymer were prepared to verify the structure of the ordered polymer. 1H and 13C NMR spectroscopy confirmed the formation of the expected polymers. The constitutional regularity of polymers influenced the crystallinity.

Synthesis and characterization of ordered polyurethanes from nonsymmetric diisocyanate and ethylene glycol

An ordered polyurethane with a head-to-head (H-H) or tail-to-tail (T-T) content over 95% was prepared by polyaddition reaction of a nonsymmetric monomer, p-isocyanatobenzyl isocyanate (1) with a symmetric monomer, ethylene glycol (2). The model reactions were studied in detail to demonstrate the feasibility of polymer formation. The polymerization was conducted in THF in the presence of triethylamine (TEA) at 0 °C by slow addition of a half amount of 2 to 1, followed by removing THF and then adding the rest of 2 in DMF at once at 30 °C in the presence of dibutyltin dilaurate (DBTL). The microstructure of the polymer obtained was investigated by 13C NMR spectroscopy, and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2106–2114, 2000

Ordered condensation polymers from symmetrical in situ and/or isolated intermediates – A review

Different syntheses of ordered condensation polymers from nonsymmetric monomers are reviewed. For several classes of polymers, the approach exploiting reactivity differences between the functional groups of the nonsymmetric monomers (ordered polymers from in situ generated intermediates) is compared with that where the relevant intermediates are used as symmetrical preformed and/or isolated precursors for the ordered polymers.

Ordered condensation polymers from symmetrical in situ and/or isolated intermediates - A review

Different syntheses of ordered condensation polymers from nonsymmetric monomers are reviewed. For several classes of polymers, the approach exploiting reactivity differences between the functional groups of the nonsymmetric monomers (ordered polymers from in situ generated intermediates) is compared with that where the relevant intermediates are used as symmetrical preformed and/or isolated precursors for the ordered polymers.

Synthesis of Ordered Polymer by Direct Polycondensation. 9. Ordered Poly(amide−acylhydrazide−amide) from Three Nonsymmetric Monomers

An ordered (−ccfebaddabef−) poly(amide−acylhydrazide−amide) was prepared by the direct polycondensation of 5-(3-carboxypropyl)-2-isopropoxybenzoic acid (XabX), bis(4-nitrophenyl) isophthalate (XccX), piperazine (YddY), and 4-aminobenzohydrazide (YefY), using the condensing agent diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1). The polymerization was carried out by mixing the dicarboxylic acid, diester, condensing agent 1, and triethylamine (TEA) in N-methyl-2-pyrrolidinone (NMP) for 3 h at room temperature, followed by adding piperazine and aminobenzohydrazide at −15 °C. The mixture was stirred at −15 °C for 2 h, room temperature for 24 h, and 70 °C for 4 d in the presence of 1-hydroxybenzotriazole (HOBt). The resulting polymer gave an inherent viscosity of 0.20 dL/g in NMP, measured at a concentration of 0.5 g/dL at 30 °C. The feasibility of the formation of the ordered polymer from three nonsymmetric monomers was demonstrated by studying the model reactions in detail. Furthermore, the authentic ordered and random polymers were prepared to verify the structure of the ordered polymer. The microstructures of the polymers obtained were investigated by 1H and 13C NMR spectroscopy, and it was found that the polymer obtained by direct polycondensation has the expected ordered structure.

Synthesis of ordered polymer by direct polycondensation. VIII. Ordered polymer from two nonsymmetric monomers

The ordered (-aacdbbdc-) polymer was prepared by the direct polycondensation of a pair of symmetric monomers (XabX), 4,4′-(oxydi-p-phenylene)dibutanoic acid (XaaX) and 2-methoxyisophthalic acid (XbbX), with a nonsymmetric monomer (YcdY), 4-aminobenzhydrazide, using the condensing agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1). The polymerization was carried out by a one-pot procedure, that is, mixing the dicarboxylic acids, condensing agent 1 and triethylamine in NMP for 2 h at room temperature, followed by the addition of 4-aminobenzhydrazide. This polymerization proceeded smoothly, yielding the ordered polymer with an inherent viscosity of 0.34 dL g−1. The microstructure of the ordered polymer was confirmed by comparing the authentic ordered polymer in their 13C-NMR spectrum. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2309–2314, 1998

Synthesis of Ordered Polymer by Direct Polycondensation. 7. Ordered Poly(acylhydrazide−amide)

An ordered (−aadcbbcd−) poly(acylhydrazide−amide) was prepared by the direct polycondensation of a pair of symmetric monomers (XabX), 2,5-dimethylterephthalic acid (XaaX) and 4,4‘-(oxydi-p-phenylene)dibutanoic acid (XbbX), with a nonsymmetric monomer (YcdY), 4-aminobenzhydrazide, using the condensing agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate (1). The polymerization was carried out by mixing the dicarboxylic acids, condensing agent 1, and triethylamine (TEA) in NMP for 2 h at room temperature, followed by adding 4-aminobenzhydrazide, yielding the ordered poly(acylhydrazide−amide) with an inherent viscosity of 0.40 dL/g. The authentic ordered polymer was prepared to verify the structure of the ordered polymer. The microstructures of polymers obtained were investigated by 13C-NMR spectroscopy, and it was found that the polymer had the expected ordered structure. Furthermore, the model reactions were studied in detail to demonstrate the feasibility of polymer formation.

Synthesis of ordered polymers by direct polycondensation

A series of ordered polymers can be prepared by direct polycondensation of nonsymmetric monomers using diphenyl(2,3-dihydro-2-oxo-3-benzothiazolyl)phosphonate ( 1) as a condensing agent. The methodology and requirements for the preparation of ordered polymer are first presented. Then, the following ordered polymer syntheses are described: (1) ordered polyamides (head-to-head or tail-to-tail) from a symmetric monomer and a nonsymmetric monomer. (2) the ordered polyamide (head-to-tail) from a symmetric monomer and a nonsymmetric monomer. (3) the ordered (-abcd-) polymer from a pair of two symmetric monomers and a nonsymmetric monomer. (4) the ordered (-abcdef-) polymer from nonsymmetric monomers, XabX, YcdY, and ZefZ.

Synthesis of Ordered Polyamides by Direct Polycondensation. 5. Ordered Poly(amide-thioether)s

An ordered (-abcd-) poly(amide-thioether) was prepared by poly(addition-direct condensation) of a pair of two nonsymmetric monomers, 4-(acryloyloxy)benzoic acid (XabX) and 4-aminobenzenethiol (YcdY), using the activating agent diphenyl(2,3-dihydro-2-thioxo-9-benzoxazolyl)phosphonate (1). The polymerization was carried out by mixing both monomers in the presence of 1 and TEA in NMP at room temperature, yielding the ordered poly(amide-thioether) with the inherent viscosity of 0.31 dL/g. The microstructure of polymers obtained was investigated by means of 13 C-NMR spectroscopy, and it has been found that the polymer obtained had the expected ordered structure

Synthesis of ordered polyamide by direct polycondensation. 4

Ordered (-aadcbbcd-) polyamides were prepared by the direct polycondensation of a pair of symmetric monomers (XabX), bi(2,4,6-trichlorophenyl) isophthalate or bis(2,4,6-trichlorophenyl) adipate (XaaX) and 5-nitroisophthalic acid (XbbX), with a nonsymmetric monomer (YcdY), 4-aminobenzohydrazide, using the activating agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate. The polycondensation was carried out by mixing the monomers all at once, yielding the ordered polyamide with inherent viscosities up to 0.30 dL/g. The authentic ordered and random polyamides were prepared to verify the structures of ordered polyamide

Synthesis of ordered polyamides by direct polycondensation. 3

Ordered (head-to-tail) polyamides with inherent viscosities up to 0.22 dL/gwere prepared by the direct polycondensation of a symmetric monomer, succinic anhydride, with a nonsymmetric monomer, 2-(4-aininophenyl)ethylainine, or a pair of two symmetric monomers, 4,4'-oxydianiline and m-xylylenediainine, using the activating agent diphenyl (2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphonate. The microstructure of the polyamides was investigated by 13 C NMR and the model reaction was studied in detail to demonstrate the feasability of ordered polyamidation

Synthesis of Sequential Polyamide by Direct Polycondensation

A convenient method for the synthesis of sequential polyamide (head-to-head, or tail-to-tail) has been developed. This polymer was prepared by the direct polycondensation of symmetric monomer (YccY), isophthalic acid (2b) with nonsymmetric monomer (XabX), 2,6-dimethyl-p-phenylenediamine (4) using the activating agent, diphenyl(2,3-dihydro-2-thioxo-3-benzoxazolyl)phosphate (1). The polycondensation was carried out by slow addition of 2b to 4, and gave the sequential (head-to-head, or tail-to-tail) polyamide (14) with inherent viscosity of 0.2 dlg−1. The authentic polyamides with different values of s (probability of –accb– placement) were prepared to verify the structure of polyamide 14. Furthermore, the model reaction was studied in detail to demonstrate the feasibility of the sequential polyamidation.

Constitutional isomerism in step‐growth polymers: Theoretical aspects of systems with two nonsymmetric monomers

AbstractA model was developed to determine the constitution of step‐growth polymers synthesized from the nonsymmetric monomers XabX and YcdY under various modes of mixing. Depending upon the inherent kinetics of the system and the modes of addition of monomers, polymer constitution can be varied over wide ranges. Results are shown for single‐stage polymerizations with all variations of kinetic parameters and mixing modes. The results show that the synthesis of truly “random” polymers is very difficult with this monomer system.