Synthesis and near infrared properties of rare earth ionomers

Fully exchanged, anhydrous ionomers of ethylene-co-acrylic acid (EAA) copolymers and ethylene-co-methacrylic acid (EMAA) copolymers containing Dy⁺³, Er⁺³, Sm⁺³, Tb⁺³, Tm⁺³, and Yb⁺³, and mixtures of them, were synthesized and studied in the near infrared region by reflection and Fourier Transform Laser Raman spectroscopies. The EAA copolymers ranged from 1.4 to 8.7 mol % acid and the EMAA copolymers were 7.3 and 16.2 mol % acid. The ionomers were shown to be essentially free of carboxylic acid groups, water, or other forms containing O (SINGLE BOND) H groups and were characterized by infrared and other methods. They are light and heat stable, and become thermoplastic and moldable at ca. 220°C under pressure. When excited at 1.064 μ with a Nd: YAG laser, these ionomers exhibit novel, lanthanide-dependent near infrared luminescence and strong Raman scattering in the near infrared region. The strongest luminescence is observed with Sm⁺³ ionomers. The Dy⁺³ ionomer Raman-shifts this source to emit light most strongly in the 1.53–1.55 μ range where the ionomer also transmits light well. © 1996 John Wiley & Sons, Inc.     

聚环氧乙烷大单体与丙烯酸乙酯的共聚及其规整接枝共聚物的表征

 本工作研完了末端为甲基丙烯酸酯型的聚环氧乙烷大单体与丙烯酸乙酯的溶液自由基共聚。结果表明,大单体接枝效率和共聚物分子量受单体总浓度、投料比、大单体分子量及引发剂等的影响,接枝效率最高可达90％以上,分子量可在5-15×10⁴范围内变化。丙烯酸乙酯与大单体共聚的竞聚率为0.83。共聚物用萃取法精制后,用IR、¹H-NMR、裂解色谱、GPC和膜渗透压计等进行了表征。证实产物有预期的规整接枝共聚物结构。平均接枝数为2—11。     

Amphiphilic PPESK-g-PEG graft copolymers for hydrophilic modification of PPESK microporous membranes

Amphiphilic graft copolymers comprising poly(phthalazinone ether sulfone ketone) (PPESK) backbones and poly(ethylene glycol) (PEG) side chains were synthesized and blended into PPESK casting solutions to prepare hydrophilic and anti-fouling microporous membranes. The graft copolymer was prepared by a modified Williamson etherification method. Sodium alkoxide of methoxyl PEG (PEG-ONa) was used to react with chloromethylated PPESK (CMPPESK). FT-IR spectroscopy, ¹H NMR and solid-state ¹³C CP-MAS NMR analysis confirmed the covalent linking of PEG with PPESK backbones. The incorporation ratio of PEG calculated from ¹H NMR was in agreement with that from TGA tests. The graft products were added into PPESK casting solutions to prepare composite porous membranes using phase inversion method. X-ray photoelectron spectroscopy (XPS) and water contact angle examinations indicated that the grafting copolymers were preferentially excluded to the membrane-coagulant interface during membrane forming, contributing the membranes with improved hydrophilicity and surface wettability. Compared with the neat membrane, the blend membranes exhibited a larger surface pore size and less susceptible to protein fouling.     

Gamma Radiation-Induced Graft Copolymerization of Styrene Onto Polyethyleneterephthalate Films: Application in Fuel Cell Technology as a Proton Exchange Membrane

Polyethyleneterephthalate (PET) based proton exchange membrane for using in fuel cells was successfully prepared by gamma radiation-induced graft copolymerization of styrene monomer onto PET film and the consequent selective sulfonation of the grafting chain in the film state using chlorosulfonic acid (ClSO₃H). The effects of grafting conditions (e.g., monomer concentration, irradiation dose) on the degree of grafting and sulfonation condition (e.g., optimum concentration of ClSO₃H) on the degree of sulfonation were studied. The degree of grafting, the degree of sulfonation and the physico-chemical properties (such as, water uptake, mechanical strength, thermal durability, hydrolytic stability, oxidative stability) of the gamma radiation-induced grafted membrane were found to be better when compared to those of the UV-radiation grafted membrane. The membrane shows higher ion exchange capacity (0.9 mmol g^?1) and higher proton conductivity (0.075 S cm^?1), similar to those of Nafion membrane.     

Development of novel cellulose acetate-g-poly(sodium 4-styrenesulfonate) proton conducting polyelectrolyte polymer

The development of cheap and efficient proton conducting polymers attracts scientists' attention, resulting in its potential role in fuel cell applications. This work synthesized a novel cellulose acetate-g-poly(sodium 4-styrene sulfonate) via free radical polymerization using potassium persulfate (KPS) as an initiator. The effects of varying KPS concentration, cellulose acetate (CA), sodium 4-styrene sulfonate (Na-SSA) content, reaction time, and temperature on the grafting parameters were studied. Grafting parameters, including the grafting yield (GY %), Add-on (%) and grafting efficiency (GE %) of the grafting reaction, were evaluated. Additionally, FTIR, TGA, DSC, ¹HNMR and EDX analyses were studied. The developed graft copolymers membranes illustrated increased water uptake values and ion exchange capacity (IEC) with the add-on (%). Furthermore, the proton conductivity of the developed graft copolymers was found superior (4.77 × 10⁻³ S.cm⁻¹) to the pristine CA membrane (0.035 × 10⁻³ S.cm⁻¹).     

Modification of poly(styrene-co-divinylbenzene) membrane by grafting of salicylic acid via a ketone bridge

Chelating solid phase extraction is a method particularly adapted to the recovery of metallic ions in polluted waters. The principle consists in the partitioning of the analyte between the solution and a solid sorbent grafted by a ligand. Aromatic organic crosslinked copolymers, which are commercially available, permit to consider numerous ways of linking the ligand to the sorbent. In this way, the grafting of salicylic acid (SA) via a ketone bridge on Amberlite^® XAD-4 resin has been previously achieved with success. Then the same grafting on Empore^™ SDB-XC membrane was also considered. The yield obtained is 33%. The determination of complexing capacities highlights the fact that about 20% of the grafted complexing sites could efficiently retain metallic ions. For the first time, a ligand has been covalently linked to Empore^™ SDB-XC membrane.     

Effects of chemical constituents on crystalline properties of ethylene ionomers

The effect of % methacrylic acid (%MAA), % neutralization (%N) and ion type (Na⁺ or Zn⁺⁺) on the crystalline properties of neutralized ethylene-methacrylic acid copolymers (ionomers) were studied using differential scanning calorimetry (DSC). Two endothermic melting peaks were observed for all the nine ionomers studied, the lower melting point (LMP) due to ordered ionic clusters and the higher melting point (HMP) due to polyethylene crystallites. Effects of %MAA, %N and ion type on LMP and HMP for as-received, aged and annealed samples are compared. Effect of types of pretreatments on LMP and HMP of ionomers at high and low %MAA contents for both ion types are discussed. Most of these results are explained from the point of view of crystalline morphology of ionomers.The author offers special thanks and appreciation to Dr. George W. Prejean of Sabine Research Laboratory, DuPont Co., Orange, Texas, for supplying the Surlyn^® ionomcrs and product nformation. Special thanks are due to Cary Evans, a senior student in the Chemical Engineering Department, for running the DSC experiments.     

Microwave-Assisted Synthesis of Poly(ε-caprolactone)-block-poly(ethylene glycol) and Poly(lactide)-block-poly(ethylene glycol)

Summary: This study reported the preparation and characterization of PCL-b-mPEG (poly(ε-caprolactone)-block-poly(ethylene glycol)) and PLL-b-mPEG (poly(L-lactide)-block-poly(ethylene glycol)) diblock copolymers by microwave heating and comparison of resulted products the ones with prepared by conventional heating. Diblock copolymers were synthesized successfully by the microwave-assisted ROP in the presence of stannous octoate (SnOct₂) as catalyst under nitrogen atmosphere in different monomer ratios. Structural and functional characterization of copolymers were performed by FTIR, ¹H-NMR and DSC. Molecular weight values were determined by GPC and also calculated from ¹H-NMR. According to the results, microwave irradiation allowed to obtain polymers with very narrow size distribution in very short reaction time. Similar polymers prepared by conventional heating were also synthesized for comparison. Molecular weight and conversion of polymers were increased by irradiation time. This change was continued until a certain time point after which no more increase was observed. It was concluded that microwave irradiation is a succesful method to obtain these diblock copolymers in very short reaction time and with a similar conversion obtained by conventional method.     

New associative EHEC‐g‐PAam copolymers: Their syntheses,characterization, and rheological behavior

The syntheses and rheological behavior of ethyl hydroxyethyl cellulose (EHEC)‐based graft‐copolymers were studied. Copolymers were prepared by grafting EHEC with acrylamide (Aam) via reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyl groups of EHEC were esterified with a carboxylic acid functional chain transfer agent (CTA) to prepare EHEC‐macroCTAs with different degrees of substitution. EHEC‐macroCTAs were characterized by ATR‐FTIR, ¹³C NMR, and SEC, and elemental analysis was used to quantify the degree of CTA substitution. EHEC‐macroCTAs with different degrees of substitution were copolymerized with acrylamide by “grafting from” technique. Formation of new cellulose‐based copolymers was comprehensively confirmed by ¹H NMR, ATR‐FTIR, and SEC measurements. Further, the associations of EHEC‐g‐PAam copolymers in water were studied at various concentrations and temperatures by means of UV–vis spectroscopy, fluorescence spectroscopy, and rheological measurements. The results indicate that copolymers have both intra and intermolecular association in water depending on the amount of grafts. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1869–1879, 2009     

An Improved Synthetic Method for Preparing Polyoxyethylene Macromers and a Study of Their Copolymerization with Alkyl Acrylates

Polyoxyethylene macromers were synthesized by polymerization of ethylene oxide in dimethylsulfoxide by using potassium napthalide in tetrahydrofuran as initiator, followed by termination with methacroyl chloride. Potassium naphthalide is more active as an initiator than sodium naphthalide. The initiator in this case was confirmed to be of the monoanionic type. The molecular weight of the macromers can be varied from 2 × 10³ to 1.2 × 10⁴with M_w/M_n = 1.07-1.12. The macromers were characterized by UV, IR, and ¹H NMR, and copolymerized with butyl acrylate, methyl acrylate, or methyl methacrylate. The grafting efficiency can reach about 90%. The graft copolymers were purified by extractions and characterized by GPC, IR, and a Bruss membrane osmometer. The average grafting number of the copolymers varied from 10 to 15.     

CERIC ION INITIATED GRAFTING ON CELLULOSE FROM BINARY MIXTURE OF ACRYLONITRILE AND METHYLACRYLATE

The Ce(IV)-ion induced grafting on cellulose from the binary mixture of acrylonitrile-methylacrylate has been investigated in heterogeneous and acidic conditions at 25 ± 0. 1°C. Various grafting parameters were evaluated as a function of molarity, feed composition, reaction time, and concentration of ceric ion at constant concentration of nitric acid in the feed. The higher fraction of acrylonitrile in the grafted chains than the feed has indicated the synergistic effect of methylacrylate taken in the feed along with acrylonitrile. IR and elemental analysis for nitrogen contents in the synthesized copolymers were used to determine the composition of the grafted copolymers. The reactivity ratios of acrylonitrile and methylacrylate have been determined by the Mayo and Lewis method and are found to be 1.45 and 0.9, respectively. The grafting parameters have shown increasing trends on varying feed composition (f_AN) from 0.25 to 0.80 and varying monomer concentration from 0. 6 to 5 4 mol dm^?3. The number of grafted moles of synthetic polymer (N_g) on cellulose were found to be dependent on molarity, feed composition, and ceric ion concentration. The experimental results have clearly indicated that maximum fraction of the feed was consumed in the formation of grafted copolymer chains in comparison to the homocopolymers and homopolymers. Estimation of ceric ion disappearance as a function of reaction time has clearly suggested that grafting on cellulose is initiated by the reactive sites generated through hydrogen ion abstraction by single electron transfer process.     

Synthesis,characterization and metal ion sorption studies of graft copolymers of cellulose with glycidyl methacrylate and some comonomers

To develop low-cost and environmentally friendly polymeric materials for enrichment, separation and remediation of metal ions from water, novel reactive graft copolymers based on cellulose extracted from pine needles were synthesized by grafting of poly(glycidyl methacrylate) alone and with comonomers acrylic acid, acrylamide and acrylonitrile by benzoyl peroxide initiation. Structural aspects of graft copolymers have been characterized by elemental analysis, FTIR, and solvent uptake behaviour. An attempt has been made to study sorption of Fe²⁺, Cu²⁺ and Cr⁶⁺ ions on candidate graft copolymers by an equilibration method and to investigate the structural aspects of graft copolymers and establish a relationship between the structural aspects of graft copolymers and metal ion uptake efficiency and selectivity.     

Patterned immobilization of biomolecules by using ion irradiation‐induced graft polymerization

A new method for biomolecular patterning based on ion irradiation‐induced graft polymerization was demonstrated in this study. Ion irradiation on a polymer surface resulted in the formation of active species, which was further used for surface‐initiated graft polymerization of acrylic acid. The results of the grafting study revealed that the surface graft polymerization using 20 vol % of acrylic acid on the poly(tetrafluoroethylene) (PTFE) film irradiated at the fluence of 1 × 10¹⁵ ions/cm² for 12 h was the optimum graft polymerization condition to achieve the maximum grafting degree. The results of the fluorescence microscopy also revealed that the optimum fluence to achieve the maximum fluorescence intensity was 1 × 10¹⁵ ions/cm². The grafting of acrylic acid on the PTFE surfaces was confirmed by a fluorescence labeling method. The grafted PTFE films were used for the immobilization of amine‐functionalized p‐DNA, followed by hybridization with fluorescently tagged c‐DNA. Biotin‐amine was also immobilized on the acrylic acid grafted PTFE surfaces. Successful biotin‐specific binding of streptavidin further confirmed the potential of this strategy for patterning of various biomolecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6124–6134, 2009     

Surface and bulk modification of polyolefins by functional aryl nitrenes as highly reactive intermediates

Aromatic azides with hindered amine light stabilizer (HALS) residues or hydrophilic groups such as glucose, sucrose and dextrine residues were synthesized and used for surface modification of polyolefins. By UV‐irradiation nitrenes were formed, which are able to react with polyolefin surfaces. By photochemical immobilization of the carbohydrates hydrophilicity of PE and PP was strongly increased (surface tensions > 44mN/m). Light stability of PP surfaces modified with HALS azides was comparable with PP, stabilised with Tinuvin 770. Bulk modification of ethylene‐propylene and ethylene‐octene copolymers was achieved by grafting nitrenes formed by thermal decomposition of azido benzoic acid. In a circulating air oven up to 1.55 wt% amino benzoic acid residues could be bonded covalently to ethylene‐propylene‐copolymers, less than half of it to ethylene‐octene‐copolymers. Reactive extrusion resulted in grafting yields of more than 50% for both types of copolymers.     

Thermal, mechanical and electrical properties on the styrene-grafted and subsequently sulfonated FEP film induced by electron beam

This paper examined the mechanical and electrical properties of poly(tetrafluoroethylene-co-hexafluoropropylene: FEP) film modified by electron beam (EB). The simultaneous irradiation method with EB was adopted for the grafting of styrene and subsequent sulfonation onto FEP film. The thermal and mechanical characteristics of the irradiated FEP film, and also those of the grafted and sulfonated FEP films, were investigated by TGA, FT-IR spectrometer, and Instron. The simultaneous irradiation with EB facilitated the homogeneous grafting, as well as a high degree of grafting with a maximum value of around 60%, thereby allowing accurate control of the degree of grafting at doses ranging from 10 to 100 kGy.The grafting or sulfonation decreased the thermal stability of FEP, whereas it considerably increased its mechanical properties. The high radiation resistance of virgin FEP up to a dose of 100 kGy enabled the sulfonation of FEP film to considerably reinforce its polymeric structures except of 10 kGy, thereby increasing its tensile strength at 30 kGy by two-fold compared to that of the virgin FEP film. The ion conductivity (IC) and ion-exchange capacity (IEC) values of the FEP membrane (125 μm thick), which were dependant on the degree of grafting, were 0.25 S cm⁻¹ and 2.4 mmol/g, respectively, at 59.2% of the degree of grafting and were superior to those of the commercialized Nafion membrane (IC, 0.12 S cm⁻¹; IEC, 0.9-1.0 mmol/g).     

Wettability of poly(styrene‐co‐acrylate) ionomers improved by oxygen‐plasma source ion implantation

The surfaces of poly(styrene‐co‐acrylic acid) copolymers and their Na‐ and Cs‐neutralized ionomers were modified by O₂‐plasma source ion implantation (PSII) treatment to improve the surface wettability. The changes in the surface wettability, composition, and structure upon the PSII treatment were examined with contact‐angle measurements and X‐ray photoelectron spectroscopy. The untreated surfaces of the acid copolymers and ionomers exhibited different surface energies; this implied clearly that the type of ion species affects the surface hydrophilicity. Also, the PSII treatment induced oxygen‐containing groups to reside on the surface and ionic groups to come out toward the surface; this made the surfaces of the ionomers more hydrophilic as compared with that of the acid copolymers. The ionomers also showed slow hydrophobic recovery. Thus, it was suggested that the reduced mobility of the polymer chain because of the presence of ionic aggregates results in restricted reorientation of oxygen‐containing groups. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1791–1797, 2003     

Membranes from poly(aryl ether)‐based ionomers containing multiblock segments of randomly distributed nanoclusters of 18 sulfonic acid groups

Multiblock copolymers 1a (M_n = 31,500–47,400) of sulfonated poly(aryl ether)s were synthesized by polycondensation of 4,4′‐difluorobenzophenone (DFBP), bis(4‐hydroxyphenyl)sulfone (BHPS), and an hydroxy‐terminated sulfonated oligomer, which was synthesized from DFBP and 2,2′,3,3′,5,5′‐hexaphenyl‐4,4′‐dihydroxybiphenyl a . The copolymerization of trimeric monomer b with DFBP and BHPS gave a series of copolymers 1b (M_n = 26,200–45,900). The copolymers were then sulfonated with chlorosulfonic acid to give ionomers 3a with hydrophilic multiblock segments and ionomers 3b with segments containing clusters of 18 sulfonic acid groups. The proton exchange membranes cast from ionomers 3a and 3b were characterized with regard to thermal stability, water uptake, proton conductivity, and morphology. Transmission electron microscopy images of 3a‐1 and 3b‐1 revealed a phase separation similar to that of Nafion that may explain their higher proton conductivities compared with randomly sulfonated copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4762–4773, 2009     

Grafting of living poly(ethylene oxide) onto polystyrene via aromatic nucleophilic displacement of activated nitro groups

Polystyrene of M?_ω = 2.2 × 10⁴ was alkylated with 4-nitrophthalimidomethyl groups as grafting sites. Several backbone polymers with various degrees of grafting sites (G = 2–100%) were prepared and characterized by elemental analysis, IR, ¹H- and ¹³C-NMR, and viscosity measurements. “Living” poly(ethylene oxide) with narrow molecular-weight distribution was prepared in the presence of 15-crown-5, and grafted onto the 4-nitrophthalimidomethylated polystyrene. The nitro displacement reaction was fast and the grafting yield was quantitative (100%). The graft copolymers are highly soluble in water and in organic solvents. The intrinsic viscosities of the graft copolymers are higher than those of the backbone polymers. The intrinsic viscosities show an initial increase followed by a decrease as the degree of grafting increase.     

Thermo-responsive microfibrillar graft copolymer based on carboxymethylagarose and N-isopropylacrylamide

Carboxymethylation of agarose with ClCH₂COOH in 2-propanol, formamide or dimethyl sulfoxide were evaluated in order to obtain water soluble derivatives. Higher yield (86%) and degree of substitution of carboxymethylation in primary alcoholic groups (0.70) were obtained using dimethyl sulfoxide. Carboxymethylagarose-g-PNIPAAm copolymers were synthesized by free radical graft copolymerization using Ce⁴⁺ and S₂O₈²⁻/TEMED as initiators via conventional or microwave-assisted methods. Carboxymethyl derivatives and graft copolymers were characterized by FT-IR and NMR spectroscopies, elemental analysis, TGA and DSC and morphology analysis by SEM and AFM. High nitrogen content (9.7%) was found with Ce⁴⁺ by conventional method and the obtained analysis allowed to confirm the NIPAAm grafting on the carboxymethylagarose chain. Thermoresponsive materials have a low critical solution temperature between 32 and 34 °C. Thermal stability increased ca. 60% with PNIPAAm grafting. Surface analysis of copolymers reveals a microfibrillar type morphology with diameter of 4–6 μm. Synthesized glycoconjugates could find applications in bioactive compounds transport in biological systems.     

Analysis and Characterization of Microwave Irradiation–Induced Graft Copolymerization of Methyl Methacrylate onto Delignified Grewia Optiva Fiber

Grafting of methyl methacrylate (MMA) onto delignified Grewia optiva fiber using ascorbic acid/H₂O₂ as an initiator was carried out under microwave irradiation. The effects of varying the microwave power, exposure time, and concentration of initiator and monomer of graft polymerization were studied to obtain maximum grafting percentage (26.54%). The experimental results showed that the optimal conditions for grafting were: exposure time, 10min; microwave power, 110 W; ascorbic acid concentration, 3.74mol/L × 10^?2; H₂O₂ concentration, 0.97mol/L × 10^?1; monomer concentration, 1.87mol/L × 10^?1. The graft copolymers were characterized by Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA).