Diether polyphenylquinoxalines. Monomers via nitro displacement–13C-NMR analysis of monomers and polymers

Bisbenzils have been prepared by nucleophilic aromatic nitro displacement reactions. These materials, some model compounds, and some polyphenylquinoxaline polymers prepared from them were rigorously analyzed by ¹³C-NMR spectroscopy. The observed chemical shifts were in excellent agreement with calculated values based on model systems. This served as the strongest evidence to support the proposed structures and gave additional intimate structural information on the polyphenylquinoxalines.     

Living cationic polymerization of vinyl monomers: Mechanism and synthesis of new polymers

This paper reviews the recent progress in our research on the living cationic polymerization of vinyl compounds by the hydrogen iodide/iodine (HI/I₂) initiating system, with emphasis on its scope, mechanism, and applications to new polymer synthesis. The scope of the living cationic polymerization has been expanded to include vinyl ethers, propenyl ethers, unsaturated cyclic ethers, and styrene derivatives as monomers. The initiation/propagation mechanism was discussed on the basis of recent direct analysis on the living system by NMR and UV/visible spectroscopy. The proposed mechanism involves a quantitative formation of Hl-vinyl ether adduct [CH₃-CH(OR)-I; l] that is by itself incapable of initiating polymerization. In the presence of iodine, however, the CH-I bond of l is electrophilically activated by iodine and living propagation occurs via the insertion of vinyl ether to the activated CH-I bond. Such living polymerizations were found to proceed in not only nonpolar but polar solvents (CH₂Cl₂) as well. Quenching the living end with amines gave polymers capped with an amino group that in turn enabled us to determine the living end concentration. Applications of the HI/I₂-initiated living process to the synthesis of new bifunctional and block polymers were also described.     

One-pot synthesis of polyrotaxanes via acyclic diene metathesis polymerization of supramolecular monomers

A one-pot synthesis of polyrotaxanes has been developed. The method employs a supramolecular monomer comprising a polymerizable ammonium salt and crown ether, in combination with dynamic ADMet polymerization. Ultimately, highly efficient complexation, polymerization, and end-capping were accomplished in a single operation to yield polyrotaxanes with M(w) up to 19.3 kDa and >80% of the repeat units being complexed.     

New monomers and polymers via Diels-Alder cycloaddition

The series of new bis(naphthalic anhydrides) was prepared through Diels-Alder cycloaddition. The Diels-Alder cycloaddition was used as a synthetic route to new phenylated monomers as well as to polymers. All polymers synthesized revealed to be soluble in a wide range of organic solvents such as toluene, THF, chloroform, and displayed high thermostability. Therefore, they can be processed easily and are promising candidates for advanced coating systems as well as for electrooptical applications.     

Controlled synthesis of thermoresponsive polymers derived from L-proline via RAFT polymerization

Well-defined polymers derived from L-proline are synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization and the amino acid-based polymers exhibit thermosensitive phase separation at lower critical solution temperatures (LCST = 15-45 degrees C) in aqueous medium.     

Formation of linear polymers with pendant vinyl groups via inclusion complex mediated polymerization of divinyl monomers

Ethylene glycol dimethacrylate (EGDMA) and ethylene glycol methacrylate 4-vinyl benzoate (EGMAVB) were shown to form 1:1 inclusion complexes with cyclodextrin and were characterized by instrumental techniques. Computational analysis showed that the bent conformation of the included divinyl monomer was more stable than its linear conformation. Complexation of the divinyl monomer with the first CD molecule offered substantial stabilization than with the second CD molecule. The vinyl group included in the CD cavity did not participate in polymerization. As a result, solvent soluble, linear polymers with pendant vinyl unsaturation per repeat unit were obtained. This was unequivocally established by the polymerization of a complex comprising CD and EGMAVB. The unreacted vinyl group can be polymerized in the subsequent step to yield cross-linked products.     

Stereoregularity and polymerization mechanism of polymethacrylonitriles determined by 13C-NMR spectroscopy

Carbon-13 nuclear magnetic resonance (¹³C-NMR) spectra of polymethacrylonitriles prepared under various conditions were measured. In acetone solution, the α-methyl carbon absorptions were split into triads and partially into pentads, and the methylene carbon absorptions into tetrads. In trifluoroacetic acid solution, the α-methyl carbon absorptions were split into pentads and the cyano carbon absorptions into triads. The triad, tetrad, and pentad tacticities determined from ¹³C-NMR spectra were compared with dyad tacticities determined from proton NMR spectra. The stereoregularity of the polymers which are γ-ray-initiated in liquid phase at temperatures near melting point (?35.8°C) and in the solid state differs from that of the polymers radically initiated at ?20 to 80°C. The stereoregularity and the conversion suggest the existence of an ionic mechanism in the polymerization at low temperatures.     

Facile synthesis of fluorescent dye labeled biocompatible polymers via immortal ring-opening polymerization

A highly efficient strategy for synthesizing "clean" fluorescent dye-labeled biocompatible polymers was established by employing a rare-earth metal catalyst via immortal ROP.     

Block polymers of isocyanates and vinyl monomers by homogeneous anionic polymerization

The “living” polymer method was used to prepare block polymers of vinyl monomers and isocyanates at low temperatures in toluene–tetrahydrofuran mixtures. Vinyl monomers and diisocyanates, which have one hindered isocyanate group, as in 2,4-toluene diisocyanate, form block polymers which contain pendant reactive isocyanate groups. These block polymers can be crosslinked with water, diols, diamines, etc. The polymerization is apparently limited to block polymer formation, since the polyisocyanate anion is incapable of initiating the polymerization of common vinyl monomers.     

The synthesis and cationic polymerization behavior of ambifunctional monomers

The synthesis of a novel series of ambifunctional monomers containing cationically polymerizable vinyl and 1-propenyl ether or 1-butenyl ether groups in the same molecule has been carried out. Studies of the onium salt-induced photopolymerizations of these monomers indicate that both functional groups are highly reactive and that they undergo extensive copolymerization. © 1996 John Wiley & Sons, Inc.     

Templated biological synthesis of polymers of abiological monomers

A general method for the in vivo incorporation of amino acid analogues into artificial proteins is described. The method involves the construction of an artificial gene encoding the sequence of interest (with the corresponding natural amino acid encoded in place of the analogue), transformation of a bacterial host strain that cannot synthesize the natural amino acid, and induction of protein synthesis in a host culture enriched in the analogue. Results are described for the amino acid analogues selenomethionine, p-fluorophenylalanine, trifluoroleucine and 3-thienylalanine.     

Functional monomers and polymers. XXXXI. Template polymerization of methacryloyl-type monomers containing nucleic acid bases

In due consideration of the specific base–base interaction that exists between nucleic acid molecules, the free radical polymerization of N-β-methacryloyloxyethyl derivatives of adenine, thymine, and theophylline initiated by azobisisobutyronitrile (AIBN) was studied in the presence of N-β-methacryloyloxyethyl-type polymers which have complementary nucleic acid bases as template polymers. The rate of polymerization of N-β-methacryloyloxyethyladenine was accelerated when poly(N-β-methacryloyloxyethyluracil) or -thymine was present in the polymerization system. The effect of the stereoregularity of the template polymers, as well as polymerization temperature and the sort of solvents used on the rate of polymerization, was studied and discussed in some detail. The results suggest that the interaction between complementary bases plays a role in template polymerization behavior.     

Solid-state 13C-NMR analysis of hypercrosslinked polystyrene

Hypercrosslinked polystyrenes, synthesized by reaction of linear or lightly crosslinked polystyrene with chloromethyl methyl ether (CME) and a Lewis acid in a good solvent, swell even in nonsolvents for polystyrene. Structures and dynamics of hypercrosslinked polystyrenes in both dry solid and solvent-swollen gel states have been determined by ¹³C-NMR spectroscopy. Deconvolution of ¹³C solid-state CP/MAS spectra gave the relative numbers of quaternary carbon atoms in monosubstituted and disubstituted benzenes. A typical sample, crosslinked by reaction of a mixture containing 0.5 mol of CME per mol of repeat units, contains 35% of unreacted and 65% of crosslinked aromatic rings, and no residual chloromethyl groups. Gels swollen in CDCl₃ and in CH₃OH have residual static dipolar interactions enabling crosspolarization and require magic angle spinning (MAS) and high power ¹H decoupling to reduce chemical shift anisotropy from ∼ 10⁴ Hz to ∼ 10³ Hz. A single proton spin-lattice relaxation time in the rotating frame measured from all peaks in the ¹³C spectra of dry samples indicates homogeneity on a nanometer scale. Proton NMR line widths indicate no substantial molecular motions in a dry hypercrosslinked polystyrene up to at least 200°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 695–701, 1997     

Living cationic polymerization of vinyl monomers: New initiators and functional polymer synthesis

This paper focuses on two recent topics in living cationic polymerization of vinyl monomers, i.e., (a) Development of new initiating systems: RCOOH/Lewis acid for vinyl ethers; CH₃CH(C₆H₅)Cl/SnCl₄/nBu₄NCl for styrene. (b) Synthesis of shape-controlled poly(vinyl ethers): Tri-armed star polymers; Multi-armed spherical polymers. For the RCOOH-based systems, a generalized concept of living cationic polymerization was discussed on the basis of the effects of the counteranions (or R) and Lewis acids (ZnCl₂ and EtAlCl₂). The CH₃CH(C₆H₅)Cl-based system permitted a truly living cationic polymerization of styrene. The tri- and multi-armed poly(vinyl ethers) included new amphiphilic polymers of unique topology, solubility, etc., all of which were prepared by living cationic polymerization.     

Helix-sense selective polymerization of carbodiimides: building permanently optically active polymers from achiral monomers

The helix-sense selective polymerization of achiral monomers by homochiral catalysts was investigated. Polymerization of chiral carbodiimides (N-(R)-2,6-(dimethylheptyl)-N'-phenylcarbodiimide) by achiral catalysts yields polymers that undergo mutorotation at elevated temperatures, thus illustrating that these chains are formed under kinetic rather than thermodynamic control. Building on this observation, the polymerization of achiral carbodiimides by (S-BINOL)Ti(OiPr)2, I, was studied. Monomers (N-hexyl-N'-(X)carbodiimide, where X = isopropyl (3), hexyl (4) or phenyl (5)), N-methyl-N'-(2-methyl-6-isopropylphenyl)carbodiimide, 6, and N-dodecyl-N'-(1-naphthyl)carbodiimide, 7, were all polymerized with I in good yields (86-95%), and all showed varying degrees of asymmetric induction. Poly-3, -4, and -5 racemized upon heating at elevated temperatures, but poly-6 and poly-7, bearing nonsymmetric phenyl groups, yielded optically active polymers that could not be racemized even at elevated temperatures. Thin films of poly-7 were found to be highly opalescent.