A simple method for determining protic end-groups of synthetic polymers by H NMR spectroscopy

A simple method for the determination of protic end-groups (-XH) in synthetic polymers involves in situ derivatization with trichloroacetyl isocyanate (TAI) in an NMR tube and observation of the imidic hydrogens of the derivatized products [-X-C(O)-NH-COCCl₃] by ¹H NMR spectroscopy. In this paper, we report that the method is effective for the quantitative determination of hydroxy, primary amino and carboxy end-groups of polymers with . It may also be applied to detect chain ends in higher molecular weight polymers. The signals for the imidic (and, in the case of amines, amidic) hydrogens appear in a region (δ 7.5-11) that is clear of other signals in the case of most aliphatic polymers and many aromatic polymers such as polystyrene and poly(ethylene terephthalate). The method has been applied in the characterization of polymers formed by conventional and living radical polymerization (RAFT, ATRP, NMP), to end functional poly(ethylene oxide) and to polyethylene-block-poly(ethylene oxide). The method appears less effective in the case of sulfanyl end-groups. The chemical shift of the imidic hydrogen shows remarkable sensitivity to the microenvironment of chain end. Thus, the imidic hydrogens of TAI derivatized polyethylene-block-poly(ethylene oxide) [PE-(EO)_mOC(O)NHC(O)CCl₃] are at least partially resolved for m=0, 1, 2, 3 and ≧4 in the 400 MHz ¹H NMR spectrum. It is also sensitive to the chain end tacticity of, for example, amino-end-functional polystyrenes and thus to the relative configuration of groups removed from the chain-end by two or more monomer units. TAI derivatization also facilitates analysis of amine functional polymers by gel permeation chromatography (GPC) which is often rendered difficult by specific interactions between the amine group and the GPC column packing.     

Spectroscopic determination of copolymer composition in high isocyanate content polymers

Copolymer compositions high in aliphatic isocyanate content cannot be determined by typical titration methods due to crosslinking during polymer workup. A quantitative method involving ultraviolet analysis of an isocyanate/absorbing amine adduct is presented. Agreement between the ultraviolet (UV) method and elemental analysis, in both composition data and reactivity ratios (r₁r₂, which are calculated from data obtained by the UV method) delineate a viable method of polymer analysis. Data from Fourier transform infrared (FTIR) analysis of the urea linkage is in good agreement with nitrogen analysis and the UV method, but is sufficiently biased to cause significant differences in r₁r₂ values. Bias in the infrared analysis may arise from the intra- or intermolecular interaction of CO and N H groups of the urea linkage. Hypochromic effects are observed in UV analysis in noncarbonylic solvents. Hypochromicity varied with copolymer composition and could be related to sequence distributions. The hypochromic effects observed were most pronounced in low amine adduct content polymers where the majority of phenyl chromophores are isolated between MMA units.     

Facile tailoring of thermal transition temperatures of epoxy shape memory polymers

A critical parameter for a shape memory polymer (SMP) lies in its shape memory transition temperature. For an amorphous SMP polymer, it is highly desirable to develop methods to tailor its T_g, which corresponds to its shape memory transition temperature. Starting with an amine cured aromatic epoxy system, epoxy polymers were synthesized by either reducing the crosslink density or introducing flexible aliphatic epoxy chains. The thermal and thermomechanical properties of these epoxy polymers were characterized by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). All the crosslinked epoxy polymers with T_g's above room temperature were found to possess shape memory properties. Overall, our approach represents a facile method to precisely tune the T_g of epoxy SMP polymers ranging from room temperature to 89 °C.     

Ionic end‐capping of (semi)telechelic polymers by mesogens

Two methods have been used to end‐cap linear polymer chains at one end or at both ends by a mesogen through ionic bonding. These polymers are designated as liquid‐crystalline halato(semi)telechelic polymers (LC H(S)TPs). The first method relies on the ion exchange reaction between the metal counterion of halato(semi)telechelic polymers and an ionic mesogen. The second method is based on the proton transfer from a sulfonic or carboxylic acid end‐group to a tertiary aliphatic amine, this approach being controlled by the relative pK_a values of the acidic and basic groups. If the pK_a difference is not large enough, strong hydrogen‐bonding is observed by Fourier‐transform infrared (FTIR) spectroscopy rather than proton transfer. The resulting materials have been characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM) and small‐angle X‐ray scattering (SAXS). © 2000 Society of Chemical Industry     

Reaction kinetics for hindered amine/epoxides by DSC

The rate constants for the reaction of two aliphatic hindered amines with phenylglycidyl ether (PGE) and the diglycidyl ether of bisphenol A (DER 332) were determined by differential scanning calorimetry (DSC). The two exothermic peaks which are present in the DSC data result from the consecutive reactions of the primary and secondary amine hydrogens and allow k₁ and k₂ to be determined. The resulting k₁/k₂ ratios obtained for these hindered amine systems are larger than the ratios previously reported for unhindered amine/epoxides.     

Understanding polymer morphology. Arthur E. Woodward. Carl Hanser Verlag,Munich, 1995. pp. ix + 130, price DM38.00. ISBN 3-446-17431-1

An investigation was undertaken regarding the adsorption of heavy metal ions (CrO^2?₄ or Pb²⁺) and phenol from solution with a highly crosslinked amphoteric starch containing the phosphate anionic group and the tertiary amine cationic group. The adsorption process was found to be dependent on initial pH and concentration for both metal ions, and to be concentration-independent for the phenol organic substance. The adsorption follows the Langmuir adsorption isotherm for CrO^2?₄, and the Freundlich adsorption isotherm for Pb²⁺. The adsorption mechanism confirms that the Na⁺ of the sodium phosphate group and the Cl^? of the tertiary amine group are used to exchange Pb²⁺ and CrO^2?₄ ions, respectively, and the tertiary amine group is used to adsorb phenol.     

Homogeneous Catalytic Cleavage of Saturated Carbon-Nitrogen Bonds

An evaluation of the catalytic reactivity of [CPD (CO)₂RuH]₂ (1) and (CPD)(CO)₃Ru (2) (where CPD = tetraphenylcyclopentadienone) with amines suggests that these complexes catalyze C-N bond cleavage by activating C-H bonds alpha to the nitrogen atom of tertiary, secondary and primary amines at ca. 140° C. When two different amines are used, transalkylation takes place. With secondary and primary amines, ammonia and tertiary amines are formed. A series of amine complexes (CPD)(CO)₂Ru.NR₃ (R = alkyl/H) was isolated from stoichiometric reactions of 1 or 2 with primary and secondary amines. It was found that tertiary amines do not generate complexes of the above type but rather unexpectedly give secondary amine complexes by cleavage of an alkyl group. The only isolatable tertiary amine complex is the moderately stable (CPD)(CO)₂RuNMe₃. All amine complexes were characterized by spectral and elemental analyses. Catalytic aspects of C-N bond cleavage were studied. Complexes (1) and (2) were found to react with primary, secondary and tertiary amines to generate imminium or eneamine species which subsequently undergo hydrolysis with water. This is in contrast to the Ru carbene mechanism previously proposed for cluster catalyzed C-N bond activation and cleavage. The two reactions are compared with respect to D for H exchange (with D₂O), water requirement and production of trace products during catalysis. A primary alcohol was found to substitute alkyl groups of a tertiary amine under the catalytic action of 1. A catalytic reaction cycle is proposed.     

Thermal degradation of montmorillonite/aliphatic amine complexes in nitrogen

Montmorillonite (Mont)/aliphatic amine complexes were synthesized using five kinds of aliphatic amine (C₂–C₁₈) hydrochlorides, and their thermal degradation below 1473 K in nitrogen was examined. Raw Mont was used as a reference. The interlayer spacings of the complexes were roughly proportional to the size of amine molecules. The five complexes showed almost the same degradation mode. All the guest amines were released from the host Mont at between 573 and 673 K without any carbon remaining, but their interlayer spacings decreased gradually up to 873 K. The layer structures of Mont and complexes were destroyed just below 1273 K. After destruction, an amorphous phase formed in Mont but not in the complexes. After heating to high temperatures, the crystals deposited in Mont were not necessarily identical to those in the complexes and these differences are attributable to the sodium content.     

Capture of carbon dioxide by an ion-exchange resin: Influence of gas humidity on capture mechanisms

This paper evaluates moisture content effects on CO₂ capture of an ion-exchange resin (IER) functionalised with a primary amine group. IER capacities were determined by breakthrough with an inlet gas containing 10 vol% CO₂, nitrogen and various moisture contents. Three types of behaviour were identified according to humidity level. In saturated air conditions, the stoichiometry could be justified by carbonates and bicarbonates fixation. In dry conditions, we suspect a joint physical adsorption and reaction mechanism. For intermediate humidity, the stoichiometry of 1 CO₂ for 1 amine group is consistent with a bicarbonate fixation or carbamic acid formation.     

Mass Spectroscopy of Vinyl Monomers Based on Stearic Acid

Mass spectra of a set of six vinyl monomers derived from stearic acid, each representative of one of the following groups: Vinyl ester (R? CO? O? CH?CH₂), allyl ester (R? CO? O? CH₂? CH?CH₂), acrylic ester (RCH₂O? CO? CH?CH₂), methacrylic ester (RCH₂O? CO? C[CH₃]?CH₂), allyl ether (RCH₂OCH₂CH?CH₂), and vinyl ether (RCH₂OCH?CH₂), where R is CH₃(CH₂)₁₆- are discussed with respect to the influence of the chemical environment on their fragment pattern.     

A new,nonphosgene route to poly(bisphenol a carbonate) by melt‐phase interchange reactions of alkylene diphenyl dicarbonates with bisphenol A

This article describes a new, nonphosgene method for the synthesis of poly(bisphenol A carbonate) (PC). The method involves three steps: the reaction of an aliphatic diol with phenyl chloroformate to form an alkylene diphenyl dicarbonate, the reaction of the alkylene diphenyl dicarbonate with bisphenol A to produce an aromatic–aliphatic polycarbonate, and the thermal treatment of the polycarbonate at 180–210°C under a stream of nitrogen with Ti(OBu)₄ to give PC and a cyclic alkylene carbonate. The method furnished low to moderate molecular masses of PC upon the complete elimination of the aliphatic moieties. The approach may be considered a new method, based on polycarbonate thermochemical degradation, for the synthesis of cyclic aliphatic carbonates. The obtained polymers were characterized by intrinsic viscosity and IR, ¹H‐NMR, and ¹³C‐NMR spectroscopy. The thermal treatment step was conducted in a glass reaction tube at 180–210°C under a stream of nitrogen, and the reaction was completed by heating to 250°C. In the thermal treatment step, semisolid effluents composed of cyclic alkylene carbonates were formed and subsequently eliminated from the reaction mixture. Heating to 250°C under nitrogen or under a dynamic vacuum furnished the pure aromatic PC residue. This intrachange reaction provides a flexible method for the synthesis of polycarbonates with alkylene diols containing two or three methylene groups, from which the pure PC homopolymer can be prepared. The potential of this approach was demonstrated by the successful synthesis of PC homopolymer from five different polycarbonates with a bisphenol A unit linked to 1,2‐propylene, 1,3‐propylene, 2‐methyl‐1,3‐propylene, 2,2‐dimethyl‐1,3‐propylene, and 1,3‐butylene as the alkane chains. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Description of the thermodynamic properties and fluid-phase behavior of aqueous solutions of linear,branched, and cyclic amines

The SAFT-γ Mie group-contribution equation of state is used to represent the fluid-phase behavior of aqueous solutions of a variety of linear, branched, and cyclic amines. New group interactions are developed in order to model the mixtures of interest, including the like and unlike interactions between alkyl primary, secondary, and tertiary amine groups (NH₂, NH, N), cyclic secondary and tertiary amine groups (cNH, cN), and cyclic methine-amine groups (cCHNH, cCHN) with water (H₂O). The group-interaction parameters are estimated from appropriate experimental thermodynamic data for pure amines and selected mixtures. By taking advantage of the group-contribution nature of the method, one can describe the fluid-phase behavior of mixtures of molecules comprising those groups over broad ranges of temperature, pressure, and composition. A number of aqueous solutions of amines are studied including linear, branched aliphatic, and cyclic amines. Liquid–liquid equilibria (LLE) bounded by lower critical solution temperatures (LCSTs) have been reported experimentally and are reproduced here with the SAFT-γ Mie approach. The main feature of the approach is the ability not only to represent accurately the experimental data employed in the parameter estimation, but also to predict the vapor–liquid, liquid–liquid, and vapor–liquid–liquid equilibria, and LCSTs with the same set of parameters. Pure compound and binary phase diagrams of diverse types of amines and their aqueous solutions are assessed in order to demonstrate the main features of the thermodynamic and fluid-phase behavior.     

Mechanism of the hydrodenitrogenation of neopentylamine and adamantylamine on sulfided NiMo/Al2O3

Neopentanethiol, 1-adamantanethiol, and 2-adamantanethiol were primary products and neopentane and adamantane were secondary products in the hydrodenitrogenation of neopentylamine, 1-adamantylamine, and 2-adamantylamine, respectively, over sulfided NiMo/Al₂O₃. Dialkylamines and dialkylimines were formed as primary products in the reactions of 2-adamantylamine and neopentylamine as well. None of the three amines can react by ammonia elimination and a classic S_N2 substitution of the NH₂ group by H₂S is not possible for the adamantylamines either. The formation of di(2-adamantyl)imine and di(neopentyl)imine indicates that dehydrogenation and hydrogenation reactions occur and that imine or iminium-cation intermediates play an important role. NH₂-SH substitution takes place by dehydrogenation of the amine to an imine or iminium cation, which adds H₂S and eliminates NH₃. The secondary character of adamantane and neopentane demonstrates that hydrogenolysis of the aliphatic C–N bond does not take place over sulfided NiMo/Al₂O₃ below 340 °C. Even though 1-adamantylamine can neither react by classic S_N2, E1, and E2 reactions, nor via an imine or iminium cation, it formed 1-adamanethiol at 300 °C. This reaction might take place by an S_N1 reaction or by adsorption of the amine at a surface vacancy, followed by a shift of the adamantyl group to a neighboring sulfur atom.     

Physical properties of aliphatic polycarbonates made from CO2 and epoxides

A homologous series of aliphatic polycarbonates with different side‐chain lengths was synthesized by ring‐opening polymerization of terminal epoxides with CO₂ using zinc adipionate as catalyst [patented process of Empower Materials (formerly PAC Polymers Inc.)]. Additionally, a polycarbonate was made having a cyclohexane unit in its backbone, together with a terpolymer having both cyclohexane and propylene units. After characterization of thermal properties the aliphatic polycarbonates were found to be completely amorphous. Polycarbonates derived from long‐chain epoxides showed a glass‐transition temperature (T_g) below room temperature, whereas polycarbonates derived from cyclohexene oxide showed a T_g of 105°C, the highest yet reported for this class of polymers. The initial decomposition temperature of the polymers in air and nitrogen atmospheres was found to be less than 300°C. The mechanical properties and the dynamic mechanical relaxation behavior of the polymers were also reported. The effect of the chemical structure on the physical properties of aliphatic polycarbonates was discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1163–1176, 2003     

Adsorption behaviors and mechanisms of porous hypercrosslinked polymers with adjustable functional groups toward doxycycline hydrochloride from water

Imino hypercrosslinked polymers (NH-HCPs), amino hypercrosslinked polymers (NH₂-HCPs), and carboxyl hypercrosslinked polymers (COOH-HCPs) were synthesized through cross-linking and Friedel-Crafts reactions to serve as highly efficient adsorbents for doxycycline hydrochloride (DOX) in water. These polymers, NH-HCPs, NH₂-HCPs, and COOH-HCPs, exhibited specific surface areas measuring 450, 267.576, and 94.39 m²/g, respectively. The adsorption kinetics of DOX onto these polymers were consistent with the pseudo-second-order model, while the adsorption isotherms followed the Langmuir model (NH-HCPs) and Freundlich model (NH₂-HCPs and COOH-HCPs), respectively. The maximum DOX adsorption capacities for NH-HCPs, NH₂-HCPs, and COOH-HCPs were 166.82, 132.43, and 72.07 mg/g, respectively. Simulation results indicated that COOH-HCPs exhibited the strongest adsorption capability due to a substantial presence of oxygen and nitrogen groups on its surface, enabling the formation of hydrogen bonds with DOX. However, its actual adsorption capacity was the lowest among the polymers, indicating that structural adjustments played a more significant role in improving adsorption performance compared to functional adjustments. Adsorption experiments conducted with NH-HCPs and NH₂-HCPs further supported this hypothesis. The primary DOX adsorption mechanism of NH-HCPs, NH₂-HCPs, and COOH-HCPs involved the H-bonding of oxygen and nitrogen functional groups, along with other mechanisms such as π-π conjugated effects, pore-filling effects, electrostatic interactions, and acid–base interactions. Overall, this study demonstrates the effectiveness of NH-HCPs, NH₂-HCPs, and COOH-HCPs in DOX removal from water, highlighting the significant influence of structural adjustments on adsorption performance.     

Development of biocompatible NaGdF4: Er3+, Yb3+ upconversion nanoparticles used as contrast agents for bio‐imaging

Upconversion nanoparticles with special fluorescence and magnetic properties have been considered an alternative contrast agent for multiple bio‐imaging techniques. It is important to understand the effects of the surface properties and dosage of upconversion nanoparticles on both the magnetic resonance (MRI) image and the photoluminescence spectrum. Here, NaGdF₄: Er³⁺, Yb³⁺ upconversion nanoparticles (UCNPs) modified with amine functional group were produced through a one‐pot thermal decomposition. The average length of the cubic UCNPs is estimated at 53 ±13 nm. The effect of the dosage of amine modified UCNPs on the MRI image is investigated. The T₁ and T₂ relaxivities of the amine modified UCNPs in agarose gel at 3 T are r₁ = 6.79 ±0.14 and r₂ = 17.0 ±0.18 (mmol/L)^?1 s^?1, which are comparable to the relaxivities of commercially available MRI contrast agents. In addition, the photoluminescence of the amine modified UCNPs at low concentrations < 150 µg/mL are further investigated with the excitation wavelength (λ_ex) at 980 nm. The internalization of the amine modified UCNPs cultured with human umbilical vascular endothelial cells (HUVEC) is observed by the fluorescence imaging. Meanwhile, T₁‐weighted MRI imaging of HUVEC cells treated with amine modified UCNPs at 10 µg/mL can be obtained. No significant toxic effect on cells is found when the concentration of the amine modified UCNPs is < 300 µg/mL. This study indicates that a low concentration of amine‐modified NaGdF₄: Er³⁺, Yb³⁺ UCNPs can be used as the contrast agent for both fluorescence imaging and magnetic resonance imaging.     

Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine) as a polychelatogen to remove toxic metals using ultrafiltration and bactericide properties of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)–Cu<Superscript>2+</Superscript> complexes

Poly(l-lysine) is a water-soluble, synthetic polypeptide containing functional amine groups that help remove di- and trivalent metal ions from aqueous solutions. This polymer’s removal properties were studied under different experimental conditions: (1) competitive and non-competitive conditions; (2) different pHs; and (3) filtration factors. Under the conditions of the Liquid-Phase Polymer-Based Retention (LPR) technique, the cooper (II) ion interaction was found to be selective and efficient when compared to other divalent metal ions studied. However, interestingly, this selectivity disappeared when trivalent metal ions were present. The polymer–metal ion interactions are based on the amino groups of the side-chains as well as the polypeptide backbone chain. The removal of metal ions was strongly dependent on the pH. By structural characterization with FT-IR and EPR spectroscopy, participation of the amide and mainly amine groups was found to take place for the coordination. For the Cu²⁺, coordination through four amine nitrogen donor atoms in the primary coordination sphere was detected. Antibacterial activity tests were conducted with the poly(l-lysine)–Cu²⁺ complex and showed a higher activity in comparison with the precursors Cu²⁺ and poly(l-lysine) at the same concentrations for E. coli (6538P), a Gram-negative bacterium, and S. aureus (ATCC), a Gram-positive bacterium.     

Comparison of the chemical structure of coal hydrogenation products,athabasca tar sand bitumen and Green River shale oil

Coal hydrogenation products, Athabasca tar sand bitumen, and Green River shale oil produced by retorting were analyzed by the Brown—Ladner method and the Takeya et al. method on the basis of elemental analysis and ¹H-NMR data, by ¹³C-NMR spectroscopy and by FT-IR spectroscopy. Structural characteristics were compared.The results show that the chemical structure of oils from Green River shale oil and Athabasca tar sand bitumen, and the oils produced in the initial stage of hydrogenation of Taiheiyo coal and Clear Creek, Utah, coal is characterized as monomers consisting of units of one aromatic ring substituted highly with C_3–6 aliphatic chains and heteroatom-containing functional groups. The chemical structure of asphaltenes from Green River shale oil and Athabasca tar sand bitumen is characterized by oligomers consisting of units of 1–2 aromatic rings substituted highly with C_3–5 aliphatic chains and heteroatom-containing functional groups. The chemical structure of asphaltenes from coal hydrogenation is characterized by dimers and/or trimers of unit structures of 2 to 5 condensed aromatic rings, substituted moderately with C_2–5 aliphatic chains and heteroatom-containing functional groups.The close agreement between fa(¹H-NMR) and fa(¹³C-NMR) for Green River shale oil derivatives and Athabasca tar sand derivatives indicates that the assumption of 2 for the atomic H/C ratio of aliphatic structures is reasonable. For coal hydrogenation products, a value of 1.6–1.7 for the H/C ratio of aliphatic structures would be more reasonable.     

Synthesis,characterization, and mechanical performance of various functionalized carbon nanotubes-polyurethanes nanocomposites

Nanocomposites of functionalized carbon nanotubes (CNTs_f) used as a reinforcement agent, and a polyurethane (PU), as a polymeric matrix were synthesized via in situ polymerization. Carbon nanotubes (CNTs) were chemically functionalized using four different chemical treatments to obtain (1) oxidized CNTs (CNTs_{OH, COOH}), (2) CNTs containing aliphatic amine groups (CNTs_{et diam}), (3) CNTs attached to an aromatic amine group (CNTs_4AB), and (4) CNTs containing a combination of aromatic amine, hydroxyl, and carboxyl functional groups (CNTs_{4AB, OH, COOH}). The nanocomposites (prepared using 0.25, 0.5 or 1.0 wt % CNTs_f) were synthesized by two processes: (1) one-step using a PU made from PCL-diol (α-ω-telechelic polyester diol) obtained by biocatalysis from ε-caprolactone (ε-CL) and diethylene glycol (DEG) and 4,4′-methylenebis (cyclohexyl isocyanate) (H₁₂MDI) in stoichiometric amounts, (2) two-step process (chain extended PU) using hexamethylene diamine (HMDA). Depending on the chemical route used to synthesized the nanocomposites, CNTs_f form, in some cases, covalent bonds and hydrogen bonding with the soft and/or hard segments of the PU matrix. Also, the presence of CNTs_f improves the thermal stability of the nanocomposites and some of their mechanical properties, compared to the pure PU properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47319.     

Regulated and non-regulated pollutants emitted from two aliphatic and a commercial diesel fuel

Two synthetic aliphatic fuels and a commercial one were used on a Diesel vehicle to study the impact on exhaust regulated and non-regulated emissions. The two aliphatic fuels decrease hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM) emissions comparing to the reference fuel (commercial fuel), but they slightly increase nitrogen oxides (NO_x) emissions. Total particle number and particle size distribution are almost the same for the three fuels used on the New European Driving Cycle (NEDC), however some differences are observed on steady speeds. The two aliphatic fuels decrease the emission of particulate sulphates, of nitrous oxide (N₂O), of carbonyl compounds and methane (CH₄) comparing to reference fuel. Carbon dioxide (CO₂) emissions of the three fuels are similar.