Houston Byrd

31P and 1H NMR studies of the transesterification polymerization of polyphosphonate oligomers

Abstract Polymeric phosphonate esters are an interesting class of organophosphorus polymers because both the polymer backbone and phosphorus substituents can be modified. These polymers have been prepared by ring-opening polymerizations of cyclic phosphites, stoichiometric polycondensations of dimethyl phosphonate with diols in conjunction with diazomethane treatment and by transesterification of polyphosphonate oligomers. Our initial attempts to prepare high molecular weight polymeric phosphonate esters by the transesterification methods were unsuccessful. Results indicate that the reactions of dimethyl phosphonate with diols to form polyphosphonate oligomers with only methyl phosphonate end groups are plagued by a serious side reaction that forms phosphonic acid end groups. These end groups do not participate in the transesterification reaction and limit the molecular weights of the polymers that can be obtained. The phosphonic acid end groups can be converted into reactive methyl phosphonate end groups by treatment with diazomethane, however diazomethane is explosive and the polymerization is slow. An alternative route for the production of high molecular weight polymers is the transesterification of the 1,12-bis(methyl phosphonato)dodecane, formed by the reaction of excess dimethyl phosphonate and 1,12-dodecanediol, with a Na 2 CO 3 promoter. This allows polymers with molecular weights of up to 4.5×10 4 to be prepared, and no phosphonic acid end groups are observed in these polymers. Thermal analyses of the poly(1,12-dodecamethylene phosphonate) have shown that this polymer has reasonable thermal stability (onset of thermal decomposition at 273 °C). This polymer also undergoes a cold crystallization process at 15 °C similar to that which has been observed in some polyesters, polyamides and elastomers.

Polycondensations of dimethyl phosphonate with diols: SEC and 1P and 13C NMR spectroscopic studies

Abstract Polymeric phosphonate esters have a variety of potential applications. These polymers can be prepared by the polycondensations of dimethyl phosphonate with certain diols. However, this method does not consistently yield high molecular weight polymers. NMR spectroscopy and size exclusion chromatography studies demonstrate that low molecular weights result from methyl group transfer from a methyl phosphonate end group to an alcohol. The inactive phosphonic acid end groups formed by this reaction can be converted into reactive methyl phosphonate end groups by treatment with diazomethane. This allows the preparation of polymers with number average molecular weights greater than 104xa0Da.

Incorporating Inorganic Extended Lattice Structures into Langmuir—Blodgett Films: Comparing Metal Phosphonate LB Films to Their Solid-State Analogs

Abstract Inorganic extended lattice structures can be incorporated into Langmuir—Blodgett (LB) films. The inorganic component not only adds lattice energy to the films, but also provides an opportunity to introduce electronic or magnetic ordering phenomena to the LB assemblies. In this Comment, LB films are described that are based on known divalent and tetravalent metal phosphonate inorganic layered solids. The LB film structures and properties are compared to the known solid-state metal phosphonates after which they are modeled. One of the films, manganese octadecylphosphonate, undergoes a magnetic ordering transition to a “weak ferromagnetic” state. It is the first example of a magnetic LB film, demonstrating how the extended lattice structure can be used to introduce new physical properties into LB films. Once the inorganic extended lattice structure is included, the possibility now exists for developing mixed organic/inorganic dual network LB films, where both the organic and inorganic networks add f...

Preparation of soluble, linear titanium-containing copolymers by the free-radical copolymerization of vinyl titanate monomers with styrene

Linear, soluble copolymers containing titanium are of interest for use in targets for inertial-confinement fusion (ICF) experiments because the titanium is a useful spectroscopic probe for studying the nuclear fusion process. Some suitable copolymers have been prepared from vinyl titanate monomers and styrene via free-radical polymerization. Soluble copolymers with molecular weights between 70,000 and 100,000 daltons containing 0.1 atom % titanium can be reliably prepared. These copolymers have been incorporated into targets used in inertial-confinement fusion experiments at Lawrence Livermore National Laboratory. Attempts to prepare identical copolymers using macromolecular modification were unsuccessful and yielded insoluble materials upon reaction of the functionalized copolymers with titanium(IV) isopropoxide.

New synthesis and structure of a polar manganese coordination polymer

A new synthesis of [N,N′-ethylenebis(salicylaldiminiato)((4-pyridylthio)acetate)] manganese(III) (Mn(Salen) polymer) has been developed, and the structure of a methanol adduct of the compound has been determined at 293 K. The compound crystallizes as an infinite chain polymer, where the Mn metal center is bridged by the (4-pyridylthio)acetate ligand. The Mn center is octahedrally coordinated with the equatorial positions being occupied by the Salen ligand. The axial positions are occupied by a pyridyl nitrogen and a carboxylate oxygen. The iteration of this bonding pattern gives the polymer a head-to-tail backbone. The major structural difference between this compound and the one previously reported occurs on the nonmetalated oxygen of the carboxylate functionality (W. Chaing, D.M. Ho, D. Van Engen, M.E. Thompson, Inorg. Chem.1993, 32, 2886; W. Chaing, Doctoral Thesis, Princeton University, Princeton, 1994). In the original structure, H2O is hydrogen bonded to the nonmetalated oxygen; however, in the structure reported here methanol is intercalated between chains without any hydrogen bonding. This indicates that this polymer can be viewed as host–guest system and that solvent plays no role in the formation of the structure.

Preparation of dichloro(2,4,6-tribromophenoxy)(1,2-diphenoxy)phosphorane and its nonoxidative chlorination reactions with alkyl and aryl phosphonates

Abstract The reaction of tetrachloro(2,4,6-tribromophenoxy)phosphorane, (TBPO)PCl 4 , with o -catechol yields dichloro(2,4,6-tribromophenoxy)(1,2-diphenoxy)phosphorane, (TBPO)(DP)PCl 2 . Quantitative 31 P[ 1 H] NMR spectroscopic studies demonstrate that this compound quantitatively converts secondary phosphonates into chlorophosphites. The chlorophosphites have been characterized by their reactions with tetracarbonylnorbornadienemolybdenum(0), Mo(CO) 4 (NBD), to form cis -Mo(CO) 4 (P(OR) 2 Cl) 2 . These reactions are also quantitative. The (TBPO)(DP)PCl 2 has major advantages over other nonoxidative chlorinating agents. The compound can be prepared in quantitative yield from stoichiometric amounts of the starting materials, the synthesis of the (TBPO)(DP)PCl 2 and the subsequent nonoxidative chlorination reaction can be carried out in one pot, and the byproduct of the reaction does not contain active chlorides.

31P{1H} NMR Studies of the Preparation of Dichlorotris(2,4,6-tribromophenoxy)phosphorane, Trichlorobis(2,4,6-tribromophenoxy)phosphorane and Tetrachloro(2,4,6-tribromophenoxy)phosphorane, and their Nonoxidative Chlorination Reactions with Dimethyl Phosphonate

Dichlorotris(2,4,6-tribromophenoxy)phosphorane can serve as a nonoxidative chlorinating agent for the conversion of secondary phosphites into chlorophosphites. However, the route reported for the synthesis of this material only gives a 22% yield, and the product contains significant impurities. To better understand the reasons for this poor yield, detailed 31P{1H} NMR studies of the reactions of phosphorus pentachloride with one, two and three equivalents of 2,4,6-tribromophenol have been carried out. These studies demonstrate that mixtures of the phosphoranes in which one, two and three of the chlorides are substituted by 2,4,6-tribromophenoxy groups are obtained even when a 3: 1 ratio of the phenol to PCl5 is used. Studies of the reactions of these mixtures with dimethyl phosphonate indicate that all three phosphoranes are equally capable of transforming dimethyl phosphonate into dimethyl chlorophosphonite in quantitative yield. The more highly substituted phosphoranes are very sensitive to water and di...