Metal‐template synthesis of cyclic epoxide–amine oligomers: Uncrosslinked epoxide–amine addition polymers, 47

The addition reaction of 2,2‐bis‐[4‐(2,3‐epoxypropoxy)‐phenyl]‐propane (DGEBA) and preformed complexes of metal ions and disecondary diamines led to a large quantity of cyclic epoxide–amine oligomers. As shown by gel permeation chromatographic analysis, cycles of n = 1, 2, and 3 were formed. Functional epoxide end groups of the prepared oligomers were completely missing in the IR and ¹H NMR and ¹³C NMR spectra. In the fast atom bombardment and matrix‐assisted laser desorption/ionization mass spectra, the molecular ions of the n = 1, 2, 3 cycles of DGEBA and N,N′‐dibenzyl‐5‐oxanonanediamine‐1,9 were detected at m/z = 680, 1361, and 2042. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2047–2052, 2003     

Synthesis and properties of π‐conjugated dithiafulvene oligomers by addition of a monofunctionalized compound

Dithiafulvene oligomers ( 3 ) were prepared by cycloaddition polymerization of aldothioketenes with their alkynethiol tautomers derived from 1,4‐diethynylbenzene ( 2 ) with the addition of 1‐ethynyl‐4‐methylbenzene ( 1 ) as a monofunctionalized compound. Different feed ratios of 2 / 1 were used to control the molecular weights of 3 . The structures of 3 were confirmed by IR and ¹H NMR spectroscopies in comparison with those of 2‐(4‐tolylidene)‐4‐tolyl‐1,3‐dithiol ( 4 ) as a model compound, which was obtained by the treatment of lithium 2‐tolylethynethiolate with water in Et₂O. The number‐average degree of polymerization (DP) and the number‐average molecular weight were measured by gel permeation chromatographic and ¹H NMR analysis. DP increased with an increasing feed ratio of 2 / 1 . The ultraviolet–visible spectra of 3 in diluted acetonitrile showed that the absorption maxima of 3 increased with an increasing DP of 3 . These redshifts are ascribed to an effective expansion of the π‐conjugation system in 3 . The oligomers exhibited a maximum conjugation length of seven repeating units. The redox properties of 3 were examined by cyclic voltammetry. The oxidation half‐peak potentials (E_p/2) of 3 were slightly cathodically shifted with increasing DP. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 708–715, 2003     

Isolation and identification of cyclic oligomers of the poly(ethylene terephthalate)–poly(ethylene isophthalate) copolymer

New cyclic oligomers of the copolymer of poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) were isolated and identified. A condensation polymerization was carried out at a high temperature, and the solid‐state polymerization that followed yielded the high molecular weight polymer. The oligomers were extracted from the high molecular weight PET–PEI copolymer and separated with preparative high performance liquid chromatography techniques. Their chemical structures and properties were analyzed and determined by ¹H NMR, differential scanning calorimetry, and mass spectroscopy. The oligomers observed at early retention times were a cyclic dimer and cyclic trimers and consisted of [GT]₃, [GI]₂, [GI]₃, [GT]₂[GI]₁, and [GT]₁[GI]₂. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 881–889, 2003     

Two‐stage copolycondensation of preformed oligomers with bisphenols by tosyl chloride/dimethylformamide/pyridine from distributions of resulting oligomers determined by a combination of gel permeation chromatography and NMR

A two‐stage co‐oligomerization of the oligomers initially formed from an equimolar mixture of isophthalic acid (IPA) and terephthalic acid (TPA) and 2,2‐bis(4‐hydroxyphenyl)propane (BPA, 50 mol %) with bisphenols (BPs, 20 mol %) was carried out using a tosyl chloride/dimethylformamide/pyridine condensing agent. The distributions of the resulting oligomers (n_x‐mers), which were quenched with methanol, were determined by a combination of gel permeation chromatography (GPC) and NMR. These distributions (presented by molar percentage) were conveniently calculated with the equation n_x (mol %) = n_x (% mol by GPC) × n₀ (mol % by NMR)/n₀ (% mol by GPC), where n_x (% mol) = n_x (wt % by GPC)/its molecular weight. The results showed the distributions of the preformed IPA/TPA‐BPA oligomers to be in fairly good accord with those obtained directly from GPC and to be supported by the NMR results. The calculation was applied to the co‐oligomers prepared up to a reaction of 0.7, at which there was an increase in the number of higher oligomers indivisible by GPC and the distributions could no longer be determined by molar percentage. The calculated distributions are discussed in relation to the results of copolycondensation. The sequence distributions in the resulting co‐oligomers, which were also examined by NMR, are compared with those in the copolymers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 44–51, 2004     

Ferrocene compounds. XXV. Synthesis and characterization of ferrocene‐containing oligoamides,their precursors,and analogues

A general method for preparation of ferrocene‐containing monoamines (5–7) and diamines (10, 11) starting from the corresponding quaternary ammonium iodide 3 and ferrocene mono‐ (4) and dithiaaliphatic acids (8, 9) was developed. Amines obtained have been characterized as acet‐ and benzamides (12–15). The oligoamide precursors (16, 17, 22, 23) were synthesized by reactions of succinic or glutaric anhydride with amines (6, 7, 10, 11). Their conversion into oligoamide analogs (20, 21, 25) failed. The desired diamides (20, 21) were prepared by condensation of amines (6, 7) with alkanedioyl chlorides, (CH₂)_n(COCl)₂ (n = 0, 1, 2, 3). Reactions of diamine 10 with succinic or glutaric anhydride gave amino acids 28—formal monomers for the planned oligomerization. Oligomers 29 were synthesized by condensation of equimolar amounts of diamines 10 and the above mentioned alkanedioyl chlorides in dichloromethane at 0°C. The structure of oligomers 29 was indicated from their IR and ¹H‐NMR spectra in comparison with the model substances 12–28. The degree of polymerization of compounds 29 was determined by ¹H‐NMR end‐group analysis (DP_n = 4–6). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 25–36, 1999     

Two novel oligomers based on fluorene and pyridine: Correlation between the structures and optoelectronic properties

To investigate the fine optoelectronic difference of the target oligomers with or without peripheral fluorene moieties, two dumbbell‐shaped oligomers ( F0 and F1 ) were designed and convergently prepared via Suzuki coupling reaction. The molecular structures of the oligomers were fully characterized by ¹H NMR, ¹³C NMR, and MALDI‐TOF mass spectra, respectively. The absorption, photoluminescent behavior, and energy band gaps of the oligomers were examined through UV–vis, photoluminescent spectra and cyclic voltammetry. The experimental results demonstrate that the absorption and photoluminescent properties are little affected by molecular architecture, while the absolute photoluminescence quantum efficiency of films and energy band gaps derived from cyclic voltammetry in solution are strongly correlated with the molecular frameworks. The observed energy band gaps of oligomers are further validated by the different molecular orbital contours of the HOMO energy levels from theoretical calculations. Preliminary electroluminescent investigations for F1 have also been conducted and discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1548–1558, 2008     

Kinetics of the ring‐opening metathesis polymerization of a 7‐oxanorbornene derivative by Grubbs' catalyst

The kinetics of the initiation and propagation of the ring‐opening metathesis polymerization of exo,exo‐5,6‐bis(methoxycarbonyl)‐7‐oxabicyclo[2.2.1]hept‐2‐ene catalyzed by Grubbs' catalyst (Cl₂(PCy₃)₂Ru?CHPh) were measured by ultraviolet–visible and ¹H NMR spectroscopy, respectively. Activation parameters for these processes were also determined. Although the ratio of the rate constant of initiation to the rate constant of propagation was determined to be less than 1 for this system, this polymerization showed many of the characteristics of a living system, including low polydispersities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2125–2131, 2003     

Copolymerization of ethylene with linear α‐olefins by 2‐phosphinophenolate nickel catalysts

2‐Dicyclohexyl‐ and 2‐diphenylphosphinophenol, CCHH and PPHH , react with Ni(1,5‐COD)₂ to form catalysts for polymerization of ethylene in or copolymerization with α‐olefins. The more P‐basic CCHH/Ni catalyst allows concentration‐dependent incorporation of olefins to give copolymers with isolated side groups and higher molecular weights, whereas the PPHH/Ni catalyst undergoes mainly stabilizing interactions with the olefins and leads to ethylene oligomers with no or marginal olefin incorporation. Pressure–time plots of the batch reactions show that the ethylene conversion is usually slower by catalysis with CCHH/Ni than by PPHH/Ni . The microstructure of the copolymers was determined by ¹³C NMR spectra, the number of side groups per main chain was estimated by ¹H NMR analyses. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 258–266, 2009     

Determination of monomers and oligomers in polyethylene terephthalate trays and bottles for food use by using high performance liquid chromatography-electrospray ionization-mass spectrometry

The types and contents of monomers and oligomers in polyethylene terephthalate (PET) food containers were analyzed using HPLC-ESI-MS after being extracted with 50% acetonitrile or dichloromethane using an accelerated solvent extraction unit. The types of cyclic oligomers were classified into first and second series. The first series represented a type of [TG]n composed of terephthalic acid (TPA; T) and monoethylene glycol (EG; G) at a ratio of 1:1. The second series showed a type of [TG]nG in which a single G unit was substituted by diethylene glycol (DEG; GG). The oligomer level extracted using dichloromethane was measured at 4024–11576 mg kg^?1. The first series cyclic oligomers, second series cyclic oligomers and linear oligomers constituted 83.0–90.6%, 7.8–14.7% and 1.3–2.8%, of the total extracted oligomers, respectively. The extracted amounts of TPA, monohydroxyethyl terephthalate and bishydroxyethyl terephthalate using 50% acetonitrile were 3.0–28.2 mg kg^?1, 16.8–118.2 mg kg^?1 and 3.9–26.7 mg kg^?1, respectively. The A2, A3, S2 and S3 groups as modified oligomers were detected as 42.9–221.4 mg kg^?1, 17.2–250.3 mg kg^?1, 1.1–48.1 mg kg^?1 and 1.0–19.8 mg kg^?1, respectively. The results of this study demonstrate an advanced analytical approach to determine the residual oligomers and monomers in PET products for food use and imply their potential migration to foodstuffs.     

Formation of linear and cyclic polyoxetanes in the cationic ring‐opening polymerization of 3‐allyloxymethyl‐3‐ethyloxetane and subsequent postpolymerization modification of poly(3‐allyloxymethyl‐3‐ethyloxetane)

The synthesis of 3‐allyloxymethyl‐3‐ethyloxetane (AllylEHO) and its polymerization with BF₃ × Et₂O is described in this study. Size exclusion chromatography (SEC) and membrane osmometry are used for the determination of molecular weights of the obtained products, ranging from M_n,SEC = 41,500‐131,500 g/mol. ¹H NMR spectroscopy, SEC, as well as MALDI‐TOF MS reveal the formation of cyclic tetramer beside low, but detectable concentrations of larger cyclic oligomers as by‐products during the polymerization process. These results help to understand mechanistically why attempts for a controlled homopolymerization of AllylEHO fail and why a controlled homopolymerization of oxetanes has not been described so far in the literature. Additionally, the high versatility of allyl‐functional polyoxetane for postpolymerization modification is proven by thiol–ene reactions with 3‐mercaptopropionic acid and N‐acetyl‐L ‐cysteine methyl ester. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Preparation,thermal properties,and flame retardance of epoxy–silica hybrid resins

A novel epoxy system was developed through the in situ curing of bisphenol A type epoxy and 4,4′‐diaminodiphenylmethane with the sol–gel reaction of a phosphorus‐containing trimethoxysilane (DOPO–GPTMS), which was prepared from the reaction of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) with 3‐glycidoxypropyltrimethoxysilane (GPTMS). The preparation of DOPO–GPTMS was confirmed with Fourier transform infrared, ¹H and ³¹P NMR, and elemental analysis. The resulting organic–inorganic hybrid epoxy resins exhibited a high glass‐transition temperature (167 °C), good thermal stability over 320 °C, and a high limited oxygen index of 28.5. The synergism of phosphorus and silicon on flame retardance was observed. Moreover, the kinetics of the thermal oxidative degradation of the hybrid epoxy resins were studied. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2354–2367, 2003     

Synthesis,characterization, and ring opening polymerization of poly(1,4‐cyclohexylenedimethylene terephthalate) cyclic oligomers

Cyclic oligomers of poly(1,4‐cyclohexylenedimethylene terephthalate) (PCT) were prepared by reaction of 1,4‐cyclohexanedimethanol (CHDM) with terephthaloyl chloride under diluted conditions and separated from the linear products by silica gel column at a yield of 23.7 wt %. Cyclic dimer, trimer, tetramer, pentamer, and hexamer were further separated by high performance liquid chromatography, and found to constitute 98% of the cyclics mixtures. The structures of PCT cyclics were confirmed by means of mass spectrometry, Fourier transform infrared, and ¹H NMR analysis. A series of experiments were carried out to study the effects of catalysts and cis/trans configuration of isomers of CHDM on the yield of cyclic oligomers. Ring opening polymerization of the cyclic oligomers was carried out by heating the sample mixtures at 310 °C for 30 min in the presence of antimony oxide. Polymerization was confirmed by inherent viscosity changes and infrared spectra of the resulting polyesters. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1828–1833, 2000     

Synthesis and characterization of fully aromatic thermotropic liquid‐crystalline copolyesters containing m‐hydroxybenzoic acid units

A series of fully aromatic copolyesters based on p‐acetoxybenzoic acid (p‐ABA), hydroquinone diacetate (HQDA), terephthalic acid (TPA), and m‐acetoxybenzoic acid (m‐ABA) were prepared by a modified melt‐polycondensation reaction. The copolyesters were characterized by DSC, thermogravimetric analysis, ¹H NMR, polarized optical microscopy, X‐ray diffraction, and intrinsic viscosity measurements. The copolyesters exhibited nematic liquid‐crystalline phases in a broad temperature range of about 150 °C, when the content of linear (p‐ABA, HQDA, and TPA) units was over 67 mol %. DSC analysis of the anisotropic copolyesters revealed broad endotherms associated with the nematic phases, and the melting or flow temperatures were found to be in the processable region. The flow temperatures and crystal‐to‐nematic and nematic‐to‐isotropic transitions depend on the type of linear monomer units, and these transitions increased as the content of the p‐ABA units increased, as compared to the HQDA/TPA units. When the content of the p‐ABA units increased, as compared to other linear units (HQDA and TPA), the intrinsic viscosity and degree of crystallinity of the copolyesters also increased, implying a higher reactivity for p‐ABA in the p‐ABA/HQDA/TPA/m‐ABA polymer system. The aromatic region in the ¹H NMR spectra of the copolyesters containing equal molar compositions of p‐ABA, HQDA, and TPA units were sensitive to the sequence distribution of aromatic rings. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3263–3277, 2001     

Synthesis and enzymatic degradation of 2‐methylene‐1,3‐dioxepane and methyl acrylate copolymers

Copolymers of 2‐methylene‐1,3‐dioxepane (MDO) and methyl acrylate (MA) containing ester units both in the backbone and as pendant groups were synthesized by free‐radical copolymerization. The influence of reaction conditions such as the polymerization time, temperature, initiator concentration, and comonomer feed ratio on the yield, molecular weight, and copolymer composition was investigated. The structure of the copolymers was confirmed by ¹H NMR, ¹³C NMR, and IR spectroscopy. Differential scanning calorimetry indicated that the copolymers had a random structure. An NMR study showed that hydrogen transfer occurred during the copolymerization. The reactivity ratios of the comonomers were r_MDO = 0.0235 and r_MA = 26.535. The enzymatic degradation of the copolymers obtained was carried out in the presence of proteinase K or a crude enzyme extracted from earthworms. The experimental results showed that the higher ester molar percentage in the backbone caused a faster degradation rate. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2898–2904, 2003     

Novel synthesis of cyclic methylvinylsiloxanes by the reaction of methylvinyl diethoxysilane with phosphorous pentachloride

We report a novel synthesis of the cyclic oligomers [(H₂C?CH)(CH₃)SiO]_n obtained by the reaction between phosphorous pentachloride and methylvinyl diethoxysilane. According to gas chromatography/mass spectrometry data, the reaction product consisted of a mixture of cyclic oligomers in which the most important fractions were composed of cycles with n = 5, 6, or 7. The reaction product was also characterized by Fourier transform infrared and ¹H and ¹³C NMR spectroscopy. Experimental results suggested a new kind of reaction between the phosphorous pentachloride and terminal olefins directly bonded to silicon, which was probably associated with sterical effects favoring C? O? Si bond cleavage of ethoxy groups instead of the conventional addition of phosphorous pentachloride to olefinic linkages. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3182–3189, 2002     

Synthesis and properties of functional aliphatic polycarbonates

Two, functional, cyclic carbonate monomers, 5‐methyl‐5‐methoxycarbonyl‐1,3‐dioxan‐2‐one and 5‐methyl‐5‐ethoxy carbonyl‐1,3‐dioxan‐2‐one, were synthesized starting from 2,2‐bis(hydroxymethyl) propionic acid. The ring‐opening polymerization of the cyclic carbonate monomers in bulk with stannous 2‐ethylhexanoate as a catalyst under different conditions was examined. The results showed that the yield and molecular weight of polycarbonates were significantly influenced by the reaction conditions. The polycarbonates obtained were characterized by IR, ¹H NMR, and differential scanning calorimetry. Their molecular weight was measured by gel permeation chromatography. The in vitro biodegradation and controlled drug‐release properties of the polycarbonates were also investigated. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 4001–4006, 2003     

New fluorinated thermoplastic elastomers. I. The synthesis and thermal characteristics of α,ω‐dihydrosilane hybrid fluorinated polysiloxane precursors

The synthesis of new α,ω‐dihydrosilane hybrid fluorinated polysiloxanes is described via the polycondensation between a diallyl perfluorinated compound and tetramethyldisiloxane. Control over the size of the oligomers is possible when the reaction is performed in two steps. The length of the polysiloxane chains influences the glass‐transition temperature and the thermal stability of the fluorinated oligomers: the higher the length is, the higher the glass‐transition temperature and the thermal stability are. The synthesized compounds have been characterized with ¹H, ¹⁹F, and ²⁹Si NMR spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4485–4492, 2002     

Crosslinked poly(ester anhydride)s based on poly(ε‐caprolactone) and polylactide oligomers

Resorbable poly(ester anhydride) networks based on ε‐caprolactone, L ‐lactide, and D,L ‐lactide oligomers were synthesized. The ring‐opening polymerization of the monomers yielded hydroxyl telechelic oligomers, which were end‐functionalized with succinic anhydride and reacted with methacrylic anhydride to yield dimethacrylated oligomers containing anhydride bonds. The degree of substitution, determined by ¹³C NMR, was over 85% for acid functionalization and over 90% for methacrylation. The crosslinking of the oligomers was carried out thermally with dibenzoyl peroxide at 120 °C, leading to polymer networks with glass‐transition temperatures about 10 °C higher than those of the constituent oligomers. In vitro degradation tests, in a phosphate buffer solution (pH 7.0) at 37 °C, revealed a rapid degradation of the networks. Crosslinked polymers based on lactides exhibited high water absorption and complete mass loss in 4 days. In ε‐caprolactone‐based networks, the length of the constituent oligomer determined the degradation: PCL5‐AH, formed from longer poly(ε‐caprolactone) (PCL) blocks, lost only 40% of its mass in 2 weeks, whereas PCL10‐AH, composed of shorter PCL blocks, completely degraded in 2 days. The degradation of PCL10‐AH showed characteristics of surface erosion, as the dimensions of the specimens decreased steadily and, according to Fourier transform infrared, labile anhydride bonds were still present after 90% mass loss. © 2003 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3788–3797, 2003     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002     

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

N‐vinyl‐2‐pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free‐radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from ¹H NMR spectra. The radical reactivity ratios for N‐vinyl‐2‐pyrrolidone (V) and methyl acrylate (M) were r_V = 0.09, r_M = 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen–Tudos and nonlinear least‐squares error‐in‐variable methods. The ¹³C{¹H} and ¹H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the ¹³C and ¹H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional ¹³C‐¹H heteronuclear single quantum correlation spectroscopic experiments. The two‐dimensional ¹H‐¹H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2225–2236, 2002