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.     

Degradation of poly[bis(ethylamino)phosphazene] in aqueous solution

Three polymers of poly[bis(ethylamino)phosphazene] (PBEAP) containing different amounts of the residual P–Cl moieties, which had been hydrolyzed into P OH in the following sample purification processes, were prepared by substitution of the chlorines on poly(dichlorophosphazene) with ethylamine. Only the polymer which had the highest side-chain content of ethylamino groups (ca. 93°_o) had a film-forming ability and a crystalline nature. The hydrolytic degradation of PBEAP in acidic solutions was investigated using the solution viscosity data obtained as a function of standing time. Acetic acid, 0.5 and 1N, pure acetic acid, and 2.2.2-trifluoroethanol were used as solvents. The degradation was composed of random breaking processes along the polymer chain, especially at the-N=P(OH)₂-and-N=P(OH)(NHC₂H₅)-units, and an unzippering-like breaking process which was started at the chain ends produced by the former random breaking. The random breaking caused an abrupt decrease in viscosity at the beginning of the degradation, and on the contrary, the unzippering-like breaking appeared as a gradual decrease in viscosity at the later stages of degradation. The total rate of degradation depended on the concentration of the ethylamino groups.     

Photochemical behaviour of poly(organophosphazenes). 14. Photooxidation of poly[bis(4-isopropylphenoxy) phosphazene] under accelerated conditions

The photooxidation of poly[bis(4-isopropylphenoxy)phosphazene] under accelerated conditions has been followed by FTIR and UV visible spectroscopic techniques. The main photooxidation products are acetophenone and phenol groups. In addition, acetone vapors have been detected by GC MS combined techniques concomitant with the IR spectral changes in the CH stretching region, suggesting a significant decrease in the isopropyl moieties. The presence of polymeric sequences having phenol groups under our conditions gives origin to further oxidation reactions due to electron transfer or radical recombination or to hydrogen abstraction reactions promoted by unhindered phenoxyl radicals. In addition, the absence of UV visible light, i.e., under thermooxidation reaction at 60° C has demonstrated that phenol groups are the main responsible of secondary oxidation products. The complexity of the photooxidation mechanism in the solid state for this polymer makes it difficult to determine a definitive degradation mechanism under both thermo- and photooxidative conditions.Presented at the 1st Italian Workshop on Cyclo- and Poly(phosphazene) Materials, February 15–16, 1996, at the CNR Research Area in Padova, Italy.See Ref. 14.     

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.     

一锅煮法合成聚二(p-乙氧羰苯氧基)磷腈

在无水K2CO3催化作用下,用一锅煮法合成了聚二(p-乙氧羰苯氧基)磷腈,产率70%,用IR3、1PNMR、1HNMR、13CNMR对其结构进行了确证,蒸汽压分子量测定法测定了数均分子量。     

Molecular dynamics simulations of polyphosphazenes: poly[bis(chloro)phosphazene][NPCl2]n

Suitable parameter sets for the CHARMm force field were derived for the structural units in polychlorophosphazene [P=N, P N, P Cl] using the Dinur Hagler energy second derivative procedure based on quantum mechanical SCI calculations using the 6–31G^* basis set. To validate the reliability of the parameter set, structural results obtained with CHARMm for the adopted model compounds (OP₂NCl₅ and OP₃N₂Cl₅) were compared with those derived fromab initio quantum mechanics using the 6–31G^* basis set. Application of molecular dynamics (MD) simulations in combinatioin with the available X-ray diffraction data provided structural and conformational information on the polymer. The calculation made using the periodic boundary conditions (PBC) agree well with the polychlorophosphazene ordered in a monoclinic unit cell (a=5.98,b=12.99,c=4.92 A; =111.7). This model was stabilized mainly by the image atoms contribution to the electrostatic energy term and had aquasi-planar conformation of the backbone chain (glide symmetry). The MD calculations also provided evidence that the difference between single and double PN bonds is less marked than that measured experimentally. This result is, however, in agreement with more recent and accurate X-ray studies on poly(methylphosphazene). Validation of the polymer model provided a complete picture, otherwise experimentally inaccessible, of the internal fluctuations of the polymeric chains.Presented at the 1st Italian Workshop on Cyclo- and Poly(phosphazene) Materials, February 15–16, 1996, at the CNR Research Area in Padova, Italy.     

Novel blends of poly[bis(glycine ethyl ester) phosphazene] and polyesters or polyanhydrides: compatibility and degradation characteristics in vitro

Poly[bis(glycine ethyl ester)phosphazene] (PGP) was blended with poly(D ,L ‐lactide) (PLA), poly(D ,L ‐lactide‐co‐glycolide) (80:20 by mole) (PLGA), poly(sebacic anhydride) (PSA) and poly(sebacic anhydride‐co‐trimellitylimidoglycine)‐block‐poly(ethylene glycol) (30:50:20 by mole) (PSTP) in various ratios using a solvent‐mixing technique. The compatibility of these blends has been evaluated by DSC, FTIR and phase contrast microscopy. The results indicated that PGP is completely incompatible with PLA, but partially compatible with PLGA and PSTP, which may be attributed to a hydrogen bonding effect. Degradation experiments have been conducted in distilled water at 37 °C and show that the blend degradation rate can be regulated by adjusting the PLGA or PSTP content of the blends. PGP/PLGA (70:30 by wt) slabs took 120 days to disappear completely, while PGP/PSTP (70:30 by wt) slabs needed only 20 days. These findings suggest that blends of PGP and PLGA or PSTP may be used as matrices for drug controlled release and for other potential biomedical applications. © 2000 Society of Chemical Industry     

Grafting reactions onto poly(organophosphazenes). VI. Thermooxidative stabilization of poly[bis (4-benzylphenoxy)phosphazene] by grafting acrylate polymers containing HALS groups

Poly[bist 4-benzylphenoxy phosphazene] is heated at 200 C in air and the oxidation of the 4-diphenylmethane side substituent to phosphazene-supported benzophenone, benzhydrol, and hydroperoxides is observed. The thermo-oxidative stabilization of the polymer is obtained by light-induced grafting copolymerization of the acrylic acid 2.2.6.6-tetramethyl-piperidin-4-yl ester onto the polyphosphazene substrate. The HALS moieties grafted onto the polyphosphazene films prevent the oxidative modification of the substituents and preserve the polymer against thermal damage. This process, investigated by IR. UV, and EPR spectroscopy, is basically dependent on the amount of HALS groups grafted onto the polyphosphazene matrix and on the composition of the reaction medium used to carry out the grafting process. The comparison between the thermooxidative stabilization process and the corresponding photooxidative stabilization reaction is also discussed.Presented at the 1st Italian Workshop on Cyclo- and Poly(phosphazene) Materials. Lebruary 15–16, 1996, at the CNR Research Area in Padova, Italy.     

3-三氟乙氧基吡啶-2-磺酰胺的合成研究

以三氟乙醇和对甲苯磺酰氯为原料,通过亲核取代、Williamson醚化、巯基化、氧化、氨化5步反应制得标题化合物,着重对醚化、巯基化反应的工艺进行优化,产品纯度98％ (HPLC).中间体及目标产物经1HNMR确认.     

Pure gas and vapor permeation properties of poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA) and its desilylated analog, poly[diphenylacetylene] (PDPA)

The permeabilities of He, H₂, N₂, O₂, CO₂, CH₄, C₂H₆, C₃H₈, and n-C₄H₁₀ in poly[1-phenyl-2-[p-(trimethylsilyl)phenyl]acetylene] (PTMSDPA) and poly[diphenylacetylene] (PDPA) are presented and compared to those of poly(1-trimethylsilyl-1-propyne) (PTMSP), poly(1-phenyl-1-propyne) (PPP), and polysulfone. Like PTMSP, PTMSDPA, a disubstituted glassy acetylene-based polymer, exhibits higher permeabilities to organic vapors than to permanent gases due to its rigid polyacetylene backbone and bulky side groups, which provide a relatively high fractional free volume (FFV) value of 0.26. Desilylation was performed on PTMSDPA. The resulting material, PDPA, is totally insoluble in common organic solvents, so it has much higher chemical resistance than PTMSDPA. Additionally, due to its insolubility in polymerization solvents, desilylation provides the only known route to high molar mass PDPA. The FFV of the resulting membrane (PDPA) is reduced by approximately 12% relative to that of PTMSDPA. This leads to a decrease in gas permeability values and selectivity of organic vapors relative to nitrogen. For example, the oxygen permeability is reduced from 1200 to 500 Barrers upon desilylation. The pure gas selectivities decrease from 9 to 3 for n-C₄H₁₀/N₂ and from 26 to 9 for C₃H₈/N₂.     

A Morphological Study of Poly[Bis(Trifluoroethoxy)Phosphazene] Using Solid-State NMR: Introducing Domain Selective 1H and 19F Decoupled 13C MAS NMR

Using solid-state NMR methods the morphological behavior of poly[bis(trifluoroethoxy)phosphazene] was studied, employing four nuclei of interest – ¹H, ¹⁹F, ³¹P and ¹³C. Measurements on all four nuclei support that at ambient temperature the crystalline and amorphous phases coexist. Variable temperature studies showed that above T(1) = 90° only a single highly mobile phase exists, which is presumed to be the 2D mesophase. All four nuclei showed that when heat cycling the polymer, repeatedly above T(1), an increase in crystallinity occurs with each cycle. For the first time ¹³C MAS NMR spectra, using high power ¹⁹F and ¹H decoupling, were obtained, which exhibited the same behaviour domain. Filtered ¹³C{¹H,¹⁹F} MAS spectra containing signal from the crystalline domain using the discrimination induced by variable amplitude minipulses (DIVAM) sequence were measured. Heat treated and solvent cast material showed differences in these ¹³C spectra, that were consistent with a decrease in backbone conformations upon heating, suggesting an increase in the extended chain form corresponding to the γ form. Analogous sensitivity to variations in crystal phase composition has not been seen previously using ¹H, ¹⁹F and ³¹P methods, emphasizing the importance of ¹³C MAS methods to morphological studies of phosphazenes. This paper is dedicated to Professor Harry R. Allcock     

A Morphological Study of Poly[bis(trifluoroethoxy)phosphazene] Using High Resolution Solid-State 1H, 19F, 31P and 13C NMR Spectroscopy

High-resolution ¹⁹F, ¹H, ³¹P and ¹³C solid-state NMR methods were assessed to ascertain their suitability for studying the morphological behavior in the crystalline domain of phosphazene polymers with partially fluorinated side-chains. Poly[bis(trifluoroethoxy)phosphazene] (PBFP) was used as a sample system. Fast magic angle spinning (MAS), along with simultaneous ¹⁹F and ¹H decoupling using the xy-16 sequence, were employed, as this has proven to greatly improve resolution in ¹³C spectra of perfluorinated materials. Information obtained from Discrimination Induced by Variable Amplitude Minipulses (DIVAM) nutation experiments and cross-polarization (CP) methods aided the deconvolution analysis used to identify all components in the ¹H, ¹⁹F and ¹³C signals. DIVAM nutation experiments were also used to discriminate between signals from the amorphous and crystalline domain. The crystallinity in the solvent-cast PBFP was determined to be approximately 70%, which was seen to increase to approximately 80% in the heat-treated material, for all nuclei studied. A preliminary assignment was made for the crystalline signals in the ¹H and ¹³C spectra to the α-, β- and γ-phases. Therefore, high-resolution ¹³C and ¹H methods are valuable tools for morphological investigations into this class of polymer.     

Synthesis,characterization, and gas transport properties of novel iptycene-based poly[bis(benzimidazobenzisoquinolinones)]

Two novel iptycene-based tetramine monomers were successfully synthesized by nucleophilic aromatic substitution of triptycene-1,4-diol and pentiptycene-6,13-diol with 5-chloro-2-nitro-aniline, followed by reduction, respectively. These monomers were polymerized with 4,4-binaphthyl-1,1,8,8-tetracarboxylic dianhydride to obtain two novel iptycene-based poly[bis(benzimidazobenzisoquinolinones)]s (PBIBI–TPD and PBIBI–PPD) by a one-step, high-temperature solution polycondesation. Incorporation of iptycene groups especially the pentiptycene group in the polymer backbones improved their solubility and thermal stability. The resulting membranes exhibited good gas permeability owing to the high internal free volume elements introduced by the iptycene groups as well as high gas selectivity due to the restricted local segmental mobility arising from the interlocking of these groups in the polymer backbone. The membrane of PBIBI–PPD showed high CO₂ permeability (112 barrer) and moderately good CO₂/N₂ and CO₂/CH₄ selectivity (22 and 31) for mixed gas separation.     

Thermal degradation mechanisms of poly[diethyl 2-(methacryloyloxy)ethyl phosphate] by Py-GC/MS

Thermal decomposition properties of poly[diethyl 2-(methacryloyloxy)ethylphosphate] (PDMP) were studied using a stepwise pyrolysis-gas chromatography/mass spectrometry (stepwise Py-GC/MS) method. The individual mass chromatograms of the various pyrolysates were correlated with the pyrolysis temperature in order to elucidate the degradation mechanisms. The scission of PDMP in helium atmosphere showed the presence of two-stage pyrolysis regions. Triethylphosphate reached maximum evolution at the initial pyrolysis temperature, indicating that scisson of PDMP was initiated by the selective cleavage at the chain end and phosphate ester side chain as the dominant pyrolysis mechanism in the first stage. This local instability at chain end and phosphate ester side chain might explain the thermal instability of PDMP at lower pyrolysis temperatures. Acetaldehyde and water, as major products, were formed in significant amounts above 300 °C, indicating that random chain scission became the dominant pyrolysis mechanism in the second stage. Thus, the random chain scission reaction favored the occurrence of crosslinking and cyclization through chain transfer of carbonization catalyzed by phosphate ester along with the evolution of the arylene-containing and cyclic compounds. From mechanism analysis of PDMP pyrolysis, the introduction of a chemically bonded phosphorous-containing pendant group could promote its fire retardancy to form the high char yield of solid residue.     

四(1,3-二氯-2-丙基)-1,2-亚乙基二磷酸酯的合成及应用

研究了以三氯氧磷、乙二醇、环氧氯丙烷为原料、TiC l4为催化剂、通过两步反应合成四(1,3-二氯-2-丙基)-1,2-亚乙基二磷酸酯阻燃剂的方法,对反应条件进行了优化。结果表明,当原料摩尔配比n乙二醇∶n三氯氧磷∶n环氧氯丙烷为1∶2.3∶4.2,反应温度分别为15~18℃、50~60℃,反应时间分别为3.5 h、4 h,催化剂用量为0.6%(与原料总量之比),制得的目标产物最好,以乙二醇计产率达92.3%。通过红外光谱和磷含量分析对产物进行了表征。用其制阻燃聚氨酯软泡,具有较好的阻燃效果。     

Synthesis and Properties of Poly[p-(2,5-dihydroxy)-phenylenebenzobisoxazole] Fiber

The novel polymer poly[p-(2,5-dihydroxy)-phenylenebenzobisoxazole] (PBOH) fiber was synthesized in the presence of 2,5-dihydroxyterephthalicacid (DHTA) and 4,6-diamino-1,3-benzenediol in poly(phosphoric acid) (PPA) using typical polycondensation conditions. The crystalline solutions of liquid PBOH in PPA were spun into fibers using dry-jet wet spinning. Furthermore, the thermostability and mechanical properties of PBOH were compared with poly(p-phenylene-2,6-benzoxazole) (PBO) in order to investigate the relationship between the chain structure and properties. The results indicated that the thermal degradation temperature of PBOH was above 750K and the tensile strength of the PBOH fiber was 3.1GPa, which were much lower than those of PBO fiber. The compressive strength of PBOH fiber was 331 M Pa, which was slightly higher than that of PBO fiber. In addition, molecular simulation was employed to explain why the compressive strength of PBOH fiber did not increase significantly compared to PBO fiber.     

Facile synthesis and characterization of novel bis(2-S-alkylpyridines) and bis(3-aminothieno[2,3-b]pyridines) incorporating 1,3-diarylpyrazole moiety

3-(4-Hydroxyphenyl)-1-phenyl-1H-pyrazole-4-carbaldehyde (1) is condensed with acetophenone to afford the corresponding unsaturated carbonyl compound 4 whose potassium salt is reacted with 1,4-dibromobutane to afford the bis-unsaturated carbonyl compound 3. Both carbonyl compounds 3 and 4 are reacted with 2-cyanoethanethioamide, through Michael addition reaction followed by cyclocondensation, to prepare the starting materials bis(pyridine-2(1H)-thione) derivative 5 and pyridine-2(1H)-thione derivative 8. Two synthetic routes to synthesize the target materials 7 and 14 are described to get the most efficient method for preparation and maximum yield%. The first route came from the direct alkylation of the bis(pyridine-2(1H)-thione) derivative 5 using iodomethane (6a) and benzyl chloride (6b) to afford the corresponding bis(2-S-alkylpyridine) derivatives 7a,b. The reaction of 5 with halo-containing compounds 10a–d to synthesize the target materials bis(3-aminothieno[2,3-b]pyridine) derivatives 14a–d failed under various reaction conditions. The second route involves the reaction of pyridine-2(1H)-thione derivative 8 with 6a,b and 10a–d to afford the corresponding 2-S-alkylpyridine derivatives 9a,b and 3-aminothieno[2,3-b]pyridine derivatives 13a–d, through the formation of 2-S-alkylpyridine derivatives 12a–d followed by a Thrope-Ziegler reaction, whose potassium salts reacted with 1,4-dibromobutane to afford the corresponding target materials 7a,b and 14a–d, respectively. The structures of target molecules were elucidated using elemental analyses and spectral data.     

Determination of electron inelastic mean free paths for poly[methyl(phenyl)silylene] films

The inelastic mean free paths (IMFPs) of electrons at a poly[methyl(phenyl)silylene] thin film surface were determined using elastic peak electron spectroscopy (EPES) and Monte Carlo calculations for a wide electron energy range, 200-1600 eV. We considered the surface composition determined from X-ray induced photoelectron spectra (XPS), the hydrogen concentration evaluated by EPES, and a correction for surface excitations. The results compare well to those calculated from the predictive TPP-2M and G1, formulae. Calculations carried out with the quantitative structure-property relationship of Cumpson and the formula of Ashley and Williams provide larger IMFP values, and can be useful only for a rough estimation.     

Aging of poly(lactide)/poly(ethylene glycol) blends. Part 2. Poly(lactide) with high stereoregularity

Blending poly(ethylene glycol) (PEG) with poly(lactide) (PLA) decreases the T_g and improves the mechanical properties. The blends have lower modulus and increased fracture strain compared to PLA. However, the blends become increasingly rigid over time at ambient conditions. Previously, it was demonstrated that a PLA of lower stereoregularity was miscible with up to 30 wt% PEG. Aging was due to slow crystallization of PEG from the homogeneous amorphous blend. Crystallization of PEG depleted the amorphous phase of PEG and gradually increased the T_g until aging essentially ceased when T_g of the amorphous phase reached the aging temperature. In the present study, this aging mechanism was tested with a crystallizable PLA of higher stereoregularity. Changes in thermal transitions, solid state structure, and mechanical properties were examined over time. Blends with up to 20 wt% PEG were miscible. Blends with 30 wt% PEG could be quenched from the melt to the homogenous amorphous glass. However, this composition phase separated at ambient temperature with little or no crystallization. Changes in mechanical properties during phase separation reflected increasing rigidity of the continuous PLA-rich phase as it became richer in PLA. Construction of a phase diagram for blends of higher stereoregular PLA with PEG was attempted.     

Synthesis and gas permeability of ester substituted poly(p-phenylene)s

Polymerizations of various ester substituted 2,5-dichlorobenzoates [substituent: linear alkyl groups (1a-f), branched alkyl groups (1g-l), cyclohexyl groups (1m-o), phenyl groups (1p-r), and oxyethylene units (1s-v)] were investigated with Ni-catalyzed/Zn-mediated system in 1-methyl-2-pyrrolidone (NMP) at 80 °C. Most of monomers bearing linear and branched alkyl groups successfully polymerized to give relatively high-molecular-weight polymers (M_n = 10,000-20,800). However, the molecular weight of the polymer having eicocyl groups was low because of steric hindrance of long alkyl chain. The polymerizations of cyclohexyl 2,5-dichlorobenzoate and phenyl 2,5-dichlorobenzoate produced low-molecular-weight polymers, while the polymerizations of monomers with alkyl cyclohexyl and alkyl phenyl groups proceeded to afford polymers with relatively high-molecular-weights. The polymers possessing oxyethylene units were obtained, but the molecular weights were low when the oxyethylene chains were long. The gas permeability of membranes of poly(p-phenylene)s with alkyl chains increased as increasing the length of alkyl chain. The membranes of poly(p-phenylene)s with phenyl groups and oxyethylene units exhibited high densities and relatively low gas permeability. However, the CO₂/N₂ separation factor of membrane of poly(p-phenylene) having oxyethylene units was as large as 73.6.