Synthesis of Poly(dichlorophosphazene) by the Melt Phase Polymerization of P-Trichloro-N-(dichlorophosphoryl)monophosphazene

A major barrier to commercialization of any of the many exciting applications of the poly(phosphazenes) has been the cost and ease of preparation of the most widely utilized starting polymer, poly(dichlorophosphazene) (Cl₂PN)_n (1). One attractive route is the thermal polycondensation reaction of P-trichloro-N-(dichlorophosphoryl)monophosphazene, Cl₃P=N–P(O)Cl₂ (2). We are reporting a modified bulk polymerization of 2 which represents a convenient route to laboratory scale amounts of (NPCl₂)_n with moderate molecular weights and polydispersity. GPC characterization data were obtained on the corresponding phenoxy derivatives, [(PhO)₂PN]_n. We also have developed a one pot synthesis of 1 from ammonium sulfate and phosphorus pentachloride which are the starting materials for the synthesis of 2 and examined the major variables, time and temperature, for this process. The resulting poly(phosphazene) exhibits more branching than the product of bulk polymerization of 1.     

Aspects of Phosphazene Research

This review reports research carried out by the authors during the last 10 years. The research involves the synthesis, characterization, functionalization, and possible utilization of cyclo- and polyphosphazenes. The investigations concern the synthesis of poly(dichlorophosphazene) by polycondensation reaction of dichlorophinoyliminotrichlorophosphorane; the grafting of unsaturated organic substrates (maleic anhydride, maleates or vinyl polymers) onto poly(organophosphazenes) by free radical reactions and the use of the synthesized materials for the preparation of new grafted copolymers or for the superficial modification of conventional organic macromolecules; the synthesis of phosphazenes containing free hydroxylic groups by reaction of methoxy aryloxy- or methoxy oligoethyleneoxy-substituted cyclo- and polyphosphazenes with boron tribromide or trimethylsilyl iodide and their use for the preparation of new phosphazene-based materials (e.g., sol-gel hybrids, thermosetting resins, azodyes, cyclolinear inorganic–organic polymers sometimes containing chiral units, or organic macromolecules having cyclophosphazene residues as pendant groups); and the preparation of oxazoline-containing cyclic and polymeric phosphazene derivatives for the synthesis of photoinitiators, chain extenders, or blend compatibilizers. The possible developments of this research are also envisaged.     

Harry R. Allcock – A True Pioneer in the Field of Inorganic and Organometallic Polymers

Selected highlights of the career of Professor Harry R. Allcock are presented. The theme of the interplay of fundamental and applied chemistry, a hallmark of Dr. Allcock’s research program, is exemplified by discussions of the mechanistic and synthetic studies of phosphazene polymerization followed by applications in the areas of biomedical materials and solid state conductivity.     

Metallo-Supramolecular Polymerization: A Route to Easy-To-Process Organic/Inorganic Hybrid Materials

The self-assembly polymerization of ditopic macromolecules via metal–ligand binding is a facile route for the preparation of metallo-supramolecular polymers (MSPs). We herein review our recent work focused on the synthesis and investigation of metallo-supramolecular polymers based on 2,6-bis(1′-methylbenzimidazolyl)pyridine endcapped poly(p-phenylene ethynylene) and poly(p-xylene) macromonomers. These materials are readily solution-processable and display appreciable mechanical properties as well as other attractive properties such as specific opto/electrical functions or high thermal stability. Our work illustrates that metallosupramolecular polymerization offers an attractive approach to assemble high-molecular-weight macromolecules from well-defined, easy to process precursors. Variation of the ditopic ligands and metal ions allows one to easily tailor the desired properties. This paper is dedicated to Professor Ian Manners and his scientific accomplishments.     

Synthesis of PCL-b-PVAc block copolymers by combination of click chemistry, ROP, and RAFT polymerizations

Abstract  

The synthesis of new poly(ε-caprolactone)(PCL)-b-poly(vinyl acetate)(PVAc) block copolymers was investigated using different combinations of click chemistry, reversible addition-fragmentation transfer (RAFT), and ring opening polymerization (ROP) techniques. Two approaches, “coupling” and “macroinitiator” routes were studied. For the coupling approach, a chain transfer agent comprising an azide function was synthesized and used as initiator for the VAc polymerization. PCL containing an alkyne termination was obtained from a bifunctional initiator bearing an alkyne function and an hydroxyl group. These two functionalized precursors, PVAc and PCL, were coupled by a 1,3 cyclo addition reaction “click chemistry” in order to obtain the corresponding block copolymer. For the macroinitiator approach, PCL-b-PVAc block copolymers were synthesized using a two-step procedure: at first, a PCL macroinitiator with a xanthate end group was prepared by coordinated anionic polymerization of ε-caprolactone; then, the RAFT polymerization of VAc was initiated from the PCL, for the preparation of PCL-b-PVAc block copolymers. Whatever the method used, no detectable quantities of unreacted PVAc or PCL were observed. ¹H NMR and size exclusion chromatography analyses indicated successful synthesis of the block copolymers with well-defined structures.     

Preparation and thermo-oxidative degradation of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)-grafted SiO<Subscript>2</Subscript> nanocomposites

Poly(l-lactic acid)/poly(l-lactic acid)-grafted SiO₂ nanocomposites were prepared by in situ melt polycondensation, in which “free” poly(l-lactic acid) and poly(l-lactic acid)-grafted SiO₂ nanoparticles were formed simultaneously. The maximum values of grafting ratio and grafting efficiency of poly(l-lactic acid) were up to 37.67% and 26.60%, respectively. In the polycondensation system, SiO₂ content was a critical parameter of getting nanocomposites with uniformly dispersed SiO₂ nanoparticles. At lower SiO₂ content, Mn of grafted poly(l-lactic acid) was close to that of “free” poly(l-lactic acid), and poly(l-lactic acid)-grafted SiO₂ nanoparticles could be well dispersed in poly(l-lactic acid) matrix. While at higher SiO₂ content, Mn of “free” poly(l-lactic acid) and grafted poly(l-lactic acid) decreased seriously, especially GPC curves of “free” poly(l-lactic acid) exhibited two peaks due to the aggregation of SiO₂ nanoparticles during the polycondensation process. The grafting ratio and SiO₂ content exhibited a clear effect on the thermo-oxidative degradation of nanocomposites. The existence of poly(l-lactic acid)-grafted SiO₂ nanoparticles dramatically improved the thermo-oxidative stability of poly(l-lactic acid). Compared with that of pure poly(l-lactic acid), T _g, T _c, and T _m of nanocomposites varied slightly.     

Performance of Φ-Sulfo Fatty Methyl Ester Sulfonate Versus Linear Alkylbenzene Sulfonate,Secondary Alkane Sulfonate and α-Sulfo Fatty Methyl Ester Sulfonate

Sulfoxidation of fatty acid methyl esters with SO_2, O₂ and ultraviolet light of appropriate wavelength, has led to the synthesis of methyl esters sulfonates or sulfoxylates, known as Φ-MES, because of the possible random position of SO₃ group in the alkyl chain. Aqueous solutions based on the sulfoxylated methyl ester of palmitic acid (Φ-MES C16) have been studied and compared to the leading types of surfactants used today: linear alkylbenzene sulfonate (LAS) secondary alkane sulfonate (SAS) and α-sulfo fatty methyl ester sulfonate (α-MES) with regard to solubility, performance and skin compatibility. The experimental results obtained indicate that Φ-MES C16 can be regarded as a potential component of detergent formulations and most likely also of body care products.

Synthesis and Reactivity of Al-MMM-2: A New Microporous/Mesoporous Catalyst for the Alkylation of Toluene

Porous, mixed-phase aluminosilicate materials containing a microporous MFI phase and a mesoporous Al-MCM-48 phase were synthesized using a one-pot synthesis method. Initially, the gemini surfactant “18-12-18” was used to form Al-MCM-48, and then the MFI template tetrapropylammonium (TPA⁺) was added to the reaction mixture at a later time. Subsequent crystallization at 150 °C led to the formation of a series of mixed-phase materials. These new materials, called “Al-MMM-2” (microporous/mesoporous materials), were characterized using powder X-ray diffraction and ²⁹Si MAS-NMR. Consistent with previous results, the amount of the microporous phase formed was dependent on the crystallization time; thus, a range of materials could be formed from a single reaction mixture. In the alkylation of toluene with benzyl alcohol, Al-MMM-2 materials showed greater structural stability, catalytic activity, and product selectivity during repeated reaction cycles, compared to either pure Al-MCM-48 or pure MFI. This article is dedicated to Professor Christopher Allen, for contributions to inorganic chemistry at the University of Vermont and for his advice, mentorship, and friendship.     

Effects of alkyl substitution on the physical properties and gas transport behavior in selected poly(R-phenoxyphosphazenes)

A systematic preparation of alkyl substituted phenoxyphosphazene polymers was performed and their gas transport properties determined. In this study, phosphazenes substituted with 4-methylphenol, 4-ethylphenol, and 4-isopropylphenol are reported. An additional polymer substituted with 4-tert-butylphenoxy-1-ethanol also was synthesized in this work. Data derived for these materials, including chemical, thermal and gas transport characterization, were compared to previous reports discussing poly[bis-phenoxyphosphazene] and its analog with tert-butyl substitution: poly[bis-(4-tert-butylphenoxy)phosphazene]. The tert-butyl moiety influences orderly chain packing, presumably through steric hindrance that can influence aromatic π-stacking. For the new poly[(alkylphenoxy)phosphazenes], semicrystallinity is maintained and the added steric bulk serves to decrease the polymer glass transition temperature (Tg) and increase both permeability and selectivity for the gas pairs: O₂/N₂ and CO₂/CH₄. Removal of the tert-butyl moiety from the immediate vicinity of the backbone through a flexible spacer serves to depress the Tg as compared to poly[bis-(4-tert-butylphenoxy)phosphazene], but provides no performance enhancement for gas transport.     

Examination of catalytic behavior and origin of the initial transient period for Pt nanoclusters modified with cinchonidine

Nanoclusters prepared by a novel water-free method are compared directly with nanoclusters prepared by the known aqueous preparation as well as conventional Pt/Al₂O₃ for the enantioselective hydrogenation of ethyl pyruvate. The catalytic behavior of cinchonidine on colloidal Pt was investigated during ethyl pyruvate hydrogenation in acetic acid under 10 bar of hydrogen at 22 °C with (1 mmol L⁻¹) and without addition of free cinchonidine. The effect of hydrogen pressure, cinchonidine concentration, ethyl pyruvate and catalyst loading on the enantiomeric excess (EE) with time were also studied. Through these studies, we propose that the nature of the observed initial transient period (ITP) for these “quasi-homogeneous” systems may be explained by desorption of the weakly adsorbed tilted “N lone pair bonded” cinchonidine species from the Pt surface due to interaction with hydrogen.     

The Promoting Effect of Tellurium on K2MoO4/SiO2 Catalyst for Methanethiol Synthesis from High H2S-Containing Syngas

Tellurium used as promoter was investigated in the preparation of K₂MoO₄/SiO₂ catalyst for methanethiol synthesis from high H₂S-containing syngas. The experimental results showed that the addition of Te to K₂MoO₄/SiO₂ improved the activity of catalysts and the selectivity of methanethiol. ESR results reveal that the addition of Te decreases the content of “oxo-Mo⁵⁺” species and increase that of the “oxysulfo-Mo⁵⁺” species, simultaneously increase the low valence states of sulfur species. XPS results reveal that the addition of Te to K₂MoO₄/SiO₂ increase the amount of low valence states of molybdenum and sulfur species, which are related to the formation of methanethiol.     

Molecular weight effect on the obtainment of parallel and perpendicular orientation in thermotropic poly(diethylene glycol <Emphasis Type="Italic">p,p′</Emphasis>-bibenzoate)

Summary The effect of molecular weight on the uniaxial orientation process has been analyzed in two samples of thermotropic poly(diethylene glycol p,p′-bibenzoate), evaluating the influence of that parameter on the type of orientation obtained. Several strain rates and deformation temperatures have been tested in order to map out the conditions for obtaining the two different kinds of orientation. The results show that in the lower molecular weight PDEB sample (M_w=31200) it is rather easy to get exclusively perpendicular “anomalous” orientation, with the molecular axes aligned transversely to the stretching direction. However, it is extremely difficult to obtain 100% parallel “normal” orientation. On the contrary, either type of orientation or a mixture of them can be easily developed for the higher molecular weight PDEB sample (M_w=102900).     

Highly oriented block copoly(ether ester) by solid state extrusion

Summary A segmented block copoly(ether ester) based on poly(butylene terephthalate) as “hard” segments and on poly(oxytetramethylene) as “soft” segments was highly oriented by cold flow extrusion. Upon further stretching of the high modulus material, the crystallites are tilted by 34∘ with respect to the stretching direction and a four point small angle X-ray pattern is obtained.     

Photochemical behavior of poly(organophosphazenes). X. Photo-cross-linking phenomena in poly[bis(4-isopropylphenoxy)0.8 (4-benzoylphenoxy)1.2 phosphazene]

The synthesis and photochemical behavior both in solution and in the solid state of poly[bis(4-isopropylphenoxy)_0.8 (4-benzoylphenoxy)_1.2 phosphazene] is described. The main reaction of this material under illumination with light of a wavelength longer than 340 nm is the intramolecular abstraction of an hydrogen atom by the excited benzophenone substituent from the 4-isopropylphenoxy moiety geminally substituted on the same phosphorus of the phosphazene chain. In this way highly reactive radical species are produced which induce very efficient photo-cross-linking of the phosphazene copolymer and insolubilization. The efficiency of this process in the solid state is examined in view of the potential application of this material as a polyphosphazene-based negative photoresist.     

Photochemical behavior of poly(organophosphazenes). X. Photo-cross-linking phenomena in poly[bis(4-isopropylphenoxy)0.8 (4-benzoylphenoxy)1.2 phosphazene]

The synthesis and photochemical behavior both in solution and in the solid state of poly[bis(4-isopropylphenoxy)_0.8 (4-benzoylphenoxy)_1.2 phosphazene] is described. The main reaction of this material under illumination with light of a wavelength longer than 340 nm is the intramolecular abstraction of an hydrogen atom by the excited benzophenone substituent from the 4-isopropylphenoxy moiety geminally substituted on the same phosphorus of the phosphazene chain. In this way highly reactive radical species are produced which induce very efficient photo-cross-linking of the phosphazene copolymer and insolubilization. The efficiency of this process in the solid state is examined in view of the potential application of this material as a polyphosphazene-based negative photoresist.     

Synthesis, characterization, thermal degradation, and comparative chain dynamics studies of weak-link polysulfide polymers

Synthesis, spectroscopic and thermal characterization of two new classes of polysulfide polymers: poly[1-(phenoxymethyl) ethylene polysulfide] (PPMEP), and poly[1-(phenoxy) ethylene polysulfide] (PPEP) is presented. The direct pyrolysis mass spectrometry (DP-MS) technique, used to study the thermal degradation behavior of these polysulfide polymers, indicated that the polymers underwent degradation through the weak-links scission. The thermal stability of the polysulfide polymers decreased as the “rank” (number of sulfur atoms in the polysulfide linkage; n = 1, 2, 4) increased. The main-chain flexibility of these polysulfide polymers in terms of their ¹³C NMR spin-lattice relaxation time (T ₁ ) measurements on the backbone methine (-CH-) and methylene (-CH₂-) carbons are reported here for the first time. A comparative study of the solution chain dynamics indicated that it increased as “rank” of the polysulfide linkages decreased as well as by introducing side chain spacers such as, ether (-O-) or methyleneoxy (-CH₂O-) groups.     

Frederic Stanley Kipping—Pioneer in Silicon Chemistry: His Life &; Legacy

Frederic Stanley Kipping FRS is regarded as one of the founding fathers of silicon chemistry. In 57 research papers published between 1899 and 1944 he reported the first use of Grignard reagents to make alkylsilanes and arylsilanes and the prepartion of silicone oligomers and polymers. He coined the term ‘silicone’ in relation to these materials in 1904. His research formed the foundation for James Franklyn Hyde’s development of the first silicon based insulation materials at Corning Glass Works and then Dow Corning Corp., as well as inspiring Eugene G. Rochow’s work at General Electric Company in the development of the ‘direct method’ of silicone synthesis using silicon hydrides. Kipping was the first Sir Jesse Boot Professor of Chemistry at Nottingham University College and was married to Lily Holland whose sisters, Mina and Kathleen were married to two other prominent early 20th century British Chemists, William H. Perkin Jr. FRS and Arthur Lapworth FRS. This paper provides an insight into Professor Kipping’s life, personality and career.     

Synthesis and Redox Properties of an Electropolymerizable Amido Ferrocenyl Pyrrole-functionalized Dendrimer

A novel diaminobutane-based poly(propyleneamine) ferrocenyl dendrimer functionalized with electrochemically polymerizable pyrrole substituents, DAB-dend-[{η⁵-C₅H₄CONH}Fe{η⁵-C₅H₄C(O)NH(CH₂)₃NC₄H₄}]₄ (1), has been prepared and characterized. A secondary reaction product, the dipyrrole derivative [Fe{η⁵-C₅H₄C(O)NH(CH₂)₃NC₄H₄}₂] (2) has been also isolated and used as a model to facilitate the characterization of 1. The molecular structure of 2 has been determined by single crystal X-ray diffraction studies. Glassy carbon electrodes have been successfully modified by electropolymerization of the pyrrole-functionalized derivatives 1 and 2, in dichloromethane/acetonitrile solutions, resulting in visually detectable electroactive ferrocenyl polymer films persistently attached to the electrode surfaces. Osteryoung square wave voltammetry experiments (OSWV) showed that films of the electropolymerized amidoferrocenylpyrrole functionalized dendrimer 1 (poly-1) senses H₂PO₄⁻ in aqueous solution using Li[B(C₆F₅)₄] as supporting electrolyte. This paper is dedicated to Professor Didier Astruc in “recognition” of his outstanding contributions to so many fields of inorganic and organic chemistry. Furthermore, CMC and BA thank him for his counsel and friendship during and after their post doctoral stages in his lab.     

Photochemical behavior of poly(organophosphazenes). XI. Photochemistry of poly[bis(4-benzylphenoxy) phosphazene]

In this paper we present results on the photolysis of poly[bis(4-benzylphenoxy)-phosphazene] in solution and in film, both in the presence and in the absence of molecular oxygen. Light irradiation of the polymer in oxygen-saturated CH₂Cl₂ solutions results in a remarkable degradation of the polyphosphazene, while in argon-purged solutions no appreciable variations of the polymer structure could be detected. The photolysis of poly[bis(4-benzylphenoxy)phosphazene] in films induces the cross-linking of the polymer regardless of the presence or the absence of molecular oxygen. The main process observed during the photochemistry both in solution and in the solid state of the polymer is the oxidation of the 4-benzylphenoxy group on the polyphosphazene, without involvement of the inorganic -P=N- backbone. The effect of temperature on the photolysis of the polyphosphazene substrate in film is also reported.     

The nutritive value of soybean oil meal prepared by the different methods of oil extraction

This article is primarily a review of the literature pertaining to the subject. Solvent extracted, hydraulic, and expeller soybean oil meals all contain, if properly cooked, protein of high biological value, similar to that of milk protein. Solvent extracted meal has a higher percentage of protein. Since expeller and hydraulic meals contain more oil than solvent extracted soybean oil meal, they naturally have a slightly higher vitamin A and D potency, but the amounts of these vitamins contained in any type of soybean meal or even in the whole soybean are not significant. Levine’s assays reveal that solvent process soybean oil meal contains roughly 2.8 I.U. of vitamin B per gram of solids compared to 1.0 I.U. for hydraulic meal. According to results of Cornell experiments, the vitamin G content of soybeans is not materially affected by any of the common methods of processing. Kraybill reports that expeller and hydraulic pressed soybean oils contain more “lecithin” (total phospholipins) than hexane extracted soybean oil. Therefore his results indicate that our domestic solvent extracted meal contains slightly more “lecithin” than expeller meal. “Lecithin” in soybean oil meal may be valuable as an antioxidant to stabilize the vitamin A contained in mixed feeds.