Two novel reactive poly(β‐cyanoethylsilsesquioxane) ( CN‐T ) and poly[(β‐cyanoethylsilsesquioxane)‐co‐(β‐methylsilsesquioxane)] ( CN‐Me‐T ) have been synthesized successfully for the first time via stepwise coupling polymerization (SCP). A variety of characterization methods including FTIR, 1H NMR, 29Si NMR, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and vapor pressure osmometry (VPO) were combined to demonstrate that the structures of the title polymers possess ordered ladder‐like structures. As expected, the ionic conductivity of these polymers mixed homogeneously with lithium perchlorate reached 10?6 S · cm?1 at room temperature and obviously increased with the raise of temperature.
Summary: A dipolar filter pulse sequence combined with cross‐polarization‐MAS is applied to characterize the phase distribution, morphology, and spin diffusion within a high‐density polyethylene sample. A new method to obtain quantitative 13C NMR by combining cross‐polarization‐MAS and spin diffusion NMR is presented. The derived crystallinity is consistent with the corresponding crystallinity obtained by 1H NMR.
Illustration of the pulse sequence(s) applied in the present work. 相似文献
A one‐pot solution polymerization under mild conditions was adapted for the synthesis of well‐defined aliphatic‐aromatic polyesters with different degrees of branching. The esterification was performed at room temperature using 4,4‐bis(4′‐hydroxyphenyl)valeric acid (AB2) and 3‐(4‐hydroxyphenyl)propionic acid (AB) as monomers. DPTS was used as a catalyst and DCC as a coupling agent. Polyesters with statistical, dendritic topology, controlled degree of branching and > 35 000 g · mol?1 were obtained. The polymers were characterized by 1H and 13C NMR, SEC, DSC, and TGA. A strong dependence of the degree of branching and the thermal properties of the polymers depending on the AB/AB2 monomer ratio was observed.
Summary: The objective of this study was to synthesize thermoplastic elastomers by the direct copolyesterification of reactive oligomers of poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] (PET) and poly(propylene oxide) (PPO). The synthesis of hard segment oligomers was achieved in two steps. The first step consisted of the glycolysis of PET leading to α,ω‐hydroxyl functionalized oligomers. The second step corresponded to the ring opening polymerization of ε‐caprolactone onto the hydroxyl end groups of the PET oligomers. Commercially available hydroxytelechelic poly(propylene oxide) was modified to obtain carboxytelechelic poly(propylene oxide). The chemical structure of the product was investigated by 1H NMR and size exclusion chromatography (SEC). Multiblock poly(ester‐ether) was then synthesized by polyesterification of hydroxytelechelic poly[(ethylene terephthalate)‐co‐(ε‐caprolactone)] with carboxytelechelic poly(propylene oxide) oligomers, using different catalysts and reaction conditions. The best stoichiometric ratio for the reaction was determined in order to obtain the highest possible . The chemical structure of the synthesized poly(ester‐ether) was investigated by size exclusion chromatography and 1H NMR. The thermal and thermomechanical behavior of the synthesized poly(ester‐ether) was investigated by differential scanning calorimetry and dynamic mechanical analysis, which showed that the poly(ester‐ether) behaved as a thermoplastic elastomer. This product could also be an interesting way for chemical recycling of PET waste.
Synthesis of multiblock co‐poly(ester‐ether). 相似文献
Summary: A novel bisphenol, (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (3FC‐PH), was synthesized via a three‐step synthetic procedure. Four aromatic polyethers based on 3FC‐PH were prepared via a nucleophilic aromatic substitution polycondensation. These polymers had a high thermal stability, and the temperatures at a 5% weight loss were above 516 °C in air. The solubility of the polyethers was improved by the introduction of bulky pendant groups. The average refractive indices of the polymer films at 1 320 nm were in the range 1.5381–1.6145. The dielectric constants of the polyether films estimated from the refractive indices were 2.69–2.98. Highly fluorinated 3FC‐PAE exhibited lower light absorption in the near‐IR region.
Summary: 1,3‐Cyclohexadiene (CHD) was homo‐ and copolymerized by means of diimine nickel complexes and various substituted titanium based half‐sandwich complexes activated with methylaluminoxane (MAO). Soluble polycyclohexadienes were produced with the constrained geometry catalyst [Me2Si(NtBu)(Me4Cp)]TiCl2 (CBT) (Cp = cyclopentadienyl, Me = methyl). Only in the presence of CBT/MAO soluble high molecular weight CHD copolymers with ethylene were obtained. The CHD incorporation was varied between 0 and 12.3 mol‐%. According to NMR analysis the CHD/ethylene copolymerization is highly regioselective, accounting for exclusive formation of 1,4‐cyclohexene units randomly distributed in the polyethylene backbone.
13C NMR spectra of 1,4‐poly(1,3‐cyclohexadiene‐co‐ethylene) with 6.8 mol‐% CHD content in the copolymer. 相似文献
1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, 13C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower Tg and higher proton conductivities. PGMA‐Tri 4 H3PO4 showed a maximum water‐free proton conductivity of approximately 10?2 S · cm?1 while that of PGMA‐ATri 2 H3PO4 was 10?3 S · cm?1. The structure and dynamics of the polymers were explored by 1H MAS and 13C CP‐MAS solid‐state NMR.
A new class of high‐performance materials, fluorinated poly(phenylene‐co‐imide)s, were prepared by Ni(0)‐catalytic coupling of 2,5‐dichlorobenzophenone with fluorinated dichlorophthalimide. The synthesized copolymers have high molecular weights ( = 5.74 × 104–17.3 × 104 g · mol?1), and a combination of desirable properties such as high solubility in common organic solvent, film‐forming ability, and excellent mechanical properties. The glass transition temperature (Tgs) of the copolymers was readily tuned to be between 219 and 354 °C via systematic variation of the ratio of the two comonomers. The tough polymer films, obtained by casting from solution, had tensile strength, elongation at break, and tensile modulus values in the range of 66.7–266 MPa, 2.7–13.5%, and 3.13–4.09 GPa, respectively. The oxygen permeability coefficients ( ) and permeability selectivity of oxygen to nitrogen ( ) of these copolymer membranes were in the range of 0.78–3.01 barrer [1 barrer = 10?10 cm3 (STP) cm/(cm2 · s · cmHg)] and 5.09–6.25, respectively. Consequently, these materials have shown promise as engineering plastics and gas‐separation membrane materials.
Summary: Advanced 1H solid‐state NMR methods are applied for studying the hydrogen bond formation occurring in polymer hydrogels based on N‐isopropylacrylamide (NIPAAm) and methacrylic acid (MAA). For P(NIPAAm‐co‐MAA) copolymers collapsed at low pH, two populations of water can be distinguished in 1H magic‐angle spinning (MAS) NMR spectra, one of which is probably situated near stable hydrogen‐bonded regions, while the other behaves similarly to free water. The pH‐induced polymer collapse can be followed in detail using 2D 1H‐1H double quantum (DQ) MAS NMR experiments on dried samples. For collapsed copolymers as well as interpenetrating polymer networks, the appearance of characteristic signals shows that hydrogen bonding takes place between NIPAAm and MMA monomers. The temperature dependence of the DQ spectra indicates that acid‐amide hydrogen bonds formed between both comonomers are more stable than the acid‐acid hydrogen bonds formed among MAA moieties alone. Correspondingly, by analyzing 1H‐1H DQ sideband patterns, a relatively short distance of 270 pm is found for the NIPAAm‐MMA hydrogen bond. Finally, the pH dependence of the DQ spectra demonstrates that hydrogen bonding phenomena are directly related to the polymer collapse.
Novel proton exchange membranes were solvent‐cast from DMF solutions of the terpolymers poly[(MA‐alt‐S)‐co‐AMPS], containing hydrophobic phenyl and reactive hydrophilic carboxylic and organo‐sulfonic acid fragments with different compositions, and PEGs with different molecular weights and amounts. These membranes were formed as a result of physical (via H‐bonding) and chemical (via PEG) cross‐linking. The structures of membranes were confirmed by FT‐IR and 1H‐ and 13C NMR spectroscopy. Mechanical and thermal properties, swellability, and proton conductivity of these membranes were significantly affected both by the chemical composition of the terpolymers (mainly the AMPS content) and also the cross‐linker (PEG) molecular weight and content in the final form of the membranes. It was concluded that the membranes prepared by using the terpolymer with an AMPS content of 36.84 mol‐% and PEG with a molecular weight of 1 450 and with an initial PEG content of 30 wt.‐% are the most suitable ones for fuel cell applications.
We present the synthesis and characterization of the compounds formed in a mixture of vinylphosphonic acid (VPA) and acetic anhydride used for the radical‐initiated VPA polymerization. High‐molecular‐weight PVPA with up to 109 000 g · mol−1 was obtained from the polymerization of a mixture containing VPA, VPAAnh, VPADiAnh and their acetylated derivatives. Relative reactivities of these compounds were estimated. The resulting polymers were characterized by viscosimetry, light scattering and NMR measurements. The complexity of the polymer structure increases with increasing anhydride content in the reaction feed as can be concluded from the 1H, 13C and 31P NMR spectra. This finding is in accordance with a cyclopolymerization mechanism resulting in five‐ and six‐membered anhydride rings within the polymer chain.
A microwave‐assisted method of synthesizing high‐molecular‐weight PLA using SSA as green catalyst was developed. Yellowish PLA with above 2.0 × 104 g · mol?1 was obtained when the reaction was run at 260 °C within 60 min under microwave irradiation with 0.4 wt.‐% SSA. This method used only 10% of the energy consumption necessary for conventional heating, and the catalyst could be used five times without losing catalytic activity. The improvement in and the decrease in the energy consumption under microwave irradiation suggested that selective heating and hot spots effects played a crucial role. The method was shown to be a time‐saving, green and a promising way to lower the cost and spread the application of PLA.
This paper describes a novel spray emulsion polymerization technique for the preparation of aqueous‐dispersible nanoscale core/shell poly(3,4‐ethylenedioxythiophene) (n‐PEDOT) colloids doped with poly[(4‐styrenesulfonic acid)‐co‐(maleic acid)] (PSS‐co‐MA). Scanning electron microscopy and transmission electron microscopy images revealed that these n‐PEDOT:PSS‐co‐MA colloids possessed sharp core/shell morphologies. X‐ray diffraction and Raman spectroscopy measurements revealed semi‐crystalline morphologies and quinoid‐dominated structures for these n‐PEDOT:PSS‐co‐MA colloids. The conductivities of n‐PEDOT and n‐PEDOT:PSS‐co‐MA pellets were ca. 3.2 and 0.29 S · cm?1, respectively, suggesting that PSS‐co‐MA acted as a shell that blocked the hopping of charges from the n‐PEDOT core to neighboring latexes. The work functions of pristine n‐PEDOT and n‐PEDOT:PSS‐co‐MA, measured using photoelectron spectroscopy, were ca. 4.7 and 5.05 eV, respectively; thus, they are close to that of indium tin oxide. The PSS‐co‐MA used in this study featured two different types of interactive functional groups, which acted as oxidative sites, dopants, and core/shell stabilizers during polymerization.
Molecular modeling is used to explain how the resistance of poly[(L ‐lactide)‐co‐(D ‐lactide)] to hydrolysis is affected by the percentages of L ‐ and D ‐lactide and their arrangements in blocks or random arrangements in the polymer. Previous studies on improving the hydrolysis resistance of PLA have involved forming either poly(L ‐lactide)/poly(D ‐lactide) (PLLA/PDLA) polyblends or copolymers of L ‐ and D ‐lactide. In this study, molecular modeling was used to study the hydrolysis resistance of PLA containing various arrangements of L ‐ and D ‐lactide in the polymers. PLA copolymers are found to have less resistance to hydrolysis than a PLLA/PDLA polyblend having the same percentages of L ‐ and D ‐lactide because a polyblend can form more stereocomplexes, which is the most stable structure PLA can form.
Poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was synthesized by cationic ring‐opening polymerization of tetrahydrofuran (THF) using a poly(3‐hexylthiophene) macroinitiator. Poly(3‐hexylthiophene) macroinitiator used for the ring‐opening polymerization of THF was synthesized by reacting the hydroxypropyl end‐group with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. 1H NMR spectroscopy and SEC data confirmed the formation of the di‐block copolymers. Field‐effect mobility of poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was measured in a thin‐film transistor configuration and was found to be 0.009 cm2 · V?1 · s?1.
Summary: Energy‐filtering transmission electron microscopy (EFTEM) was employed for the analysis of polymer‐polymer interfaces. To attain imaging and spectral analyses with a spatial resolution of 10 nm, problems arising in the EFTEM analysis for polymer specimens were investigated. Interfaces in poly(methyl methacrylate)/polystyrene‐co‐polyacrylonitrile random copolymer (PMMA/SAN) bilayer films annealed at different temperatures were analyzed by means of elemental mapping and Image‐EELS on EFTEM and the effect of the annealing temperature on the interfacial structures was also investigated.
A novel graft copolymer is synthesized from commercially available poly(vinyl alcohol) using ring‐opening polymerization. For the polymerization reaction of novel brush‐like poly(vinyl alcohol)‐graft‐poly(?‐caprolactone‐co‐(3‐/7‐(prop‐2‐ynyl)oxepan‐2‐one) 5 Sn(Oct)2 is used as a catalyst. The formation of the graft copolymer is confirmed by 1H NMR, 13C NMR, and Fourier transform infrared (FTIR) spectroscopy. Furthermore, the modification of the novel synthesized graft copolymer via a “click” reaction to implement adamantane groups is described. The success of the “click” reaction is proven by 1H NMR spectroscopy and visualized by decomplexation of cyclodextrin with included phenolphthalein.
Summary: Solid‐state 2H NMR spectroscopy was used to examine the chain dynamics of perdeuterated poly(oxyethylene) (d‐POE) inside α‐cyclodextrin (α‐CD) nanotubes. The nanotubes were prepared by aqueous self‐assembly of α‐CD onto either low‐molecular‐weight (1.5 kg/mol) or high‐molecular‐weight (25.8 kg/mol) monodisperse d‐POE. At a given temperature, POE chain segments exhibit faster dynamics when included inside the CD nanotubes as compared to the bulk. Even at 150 K, when no large‐angle dynamics are detected in bulk POE, evidence for chain motions in the nanotube‐confined POE is observed. The 2H line shapes representing this motion were modeled by a discrete 3‐site jump using a ln‐Gaussian distribution of correlation times. An activation energy of 15 ± 1 kJ/mol was determined and the motion envisioned as gauche defects propagating along the primarily trans chains included within CD nanotubes. As the nanotube length decreased, the jump angle became much less defined and more isotropic motions were observed for POE segments at elevated temperatures (>270 K).
Aniline‐based disulfide, 5‐amino‐1,4‐dihydrobenzo[d]‐1′,2′‐dithiadiene (DTAn), was synthesized through a new route. The DTAn/aniline copolymers [P(DTAn‐co‐An)] were prepared by chemical oxidative polymerization. The results show that the polymerization activity of the DTAn is obviously lower than that of aniline, and the degree of polymerization increases with the increasing feed ratio of aniline and oxidant dosage. The cyclic voltammograms of the copolymers indicate that intramolecular self‐catalyzed effects occurred between the conducting backbone and the S‐S side chain. The charge–discharge tests of Li/P(DTAn‐co‐An) cell show an initial specific capacity of 262 mAh · g−1, which suggests that P(DTAn‐co‐An) may be a promising cathode material in secondary lithium batteries.
This paper reports the assignment of the 13C NMR resonances of the Sββ and Sαγ methylenes observed in the spectra of copolymers of propylene with trace amounts of enriched ethylene‐1‐13C. The assignment is achieved by comparing the chemical shifts calculated by an empirical method (at the CH2 stereochemical pseudohexad level), with the experimental spectra of regioregular copolymers with different stereochemical structure. The implications of the observed Sββ and Sαγ resonances on the stereochemical polymerization mechanisms are also discussed.
