Crystallization of polystyrene–poly(ethylene oxide) multiblock copolymers

The heat of fusion of poly(ethylene oxide) blocks has been measured by DSC on twelve polystyrene–poly(ethylene oxide) multiblock (AB)_n copolymers and two ABA triblock copolymers after conditioning at various times and temperatures. Regardless of the length of polystyrene blocks, copolymers with poly(ethylene oxide) blocks with M?_n = 404 showed no heat of fusion, those with M?_n = 900 almost no peaks, those with M?_n = 1960 small broad peaks, and those with M?_n = 5650 clearly observable peaks. the greatest heat of fusion measured for block copolymers was 60–70% of the value for hompolymer. Small-angle x-ray patterns are given. The relation between crystal growth and block length is discussed.     

Synthesis and characterization of novel alternating fluorinated copolymers bearing oligo(ethylene oxide) side chains

The synthesis and characterization of novel poly(CTFE‐g‐oligoEO) graft copolymers [chlorotrifluoroethylene (CTFE) and ethylene oxide (EO)] are presented. First, vinyl ether monomers bearing oligo(EO) were prepared by transetherification of ω‐hydroxyoligo(EO) with ethyl vinyl ether catalyzed by a palladium complex in 70–84% yields. Two vinyl ethers of different molecular weights (three and 10 EO units) were thus obtained. Then, radical copolymerization of the above vinyl ethers with CTFE led to alternating poly(CTFE‐alt‐VE) copolymers that bore oligo(OE) side chains in satisfactory yields (65%). These original poly(CTFE‐g‐oligoEO) graft copolymers were characterized by ¹H, ¹⁹F, and ¹³C NMR spectroscopy. Their molecular weights reached 19,000 g mol^?1, and their thermal properties were investigated while their glass transition temperatures ranged between ?42 and ?36 °C. Their thermogravimetric analyses under air showed decomposition temperatures of 270 °C with 10% weight loss (T_d,10%). These novel copolymers are of potential interest as polymer electrolytes in lithium ion batteries, showing room temperature conductivities ranging from 4.49 × 10^?7 to 1.45 × 10^?6 S cm^?1 for unplasticized material. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Photopolymerization kinetics of oligo(ethylene oxide) and oligo(methylene) oxide dimethacrylates

The influence of temperature on the photopolymerization kinetics of oligo(methylene) oxide and oligo(ethylene oxide) dimethacrylate series has been investigated by isothermal DSC. The DSC curves showed a rapid rise in rate due to the Trommsdorff effect, and then a slow decline. A shoulder, apparent on many of the DSC curves at low conversions, became more prominent when the cure temperature was lowered. The kinetics were relatively insensitive to the dimethacrylate structure in the early stages of the reaction, but became more dependent as the reaction proceeded. A previously derived mathematical model, which allows for the influence of diffusion on the rate constants, was used to predict the kinetics. The dependence of the maximum rate and conversion on the curing temperature were adequately described by the model. The experimentally observed shoulder on the rate curve was also predicated as was the evolution of the rate/time curves with curing temperature. Similar predictions were found when a nonsteady state version of the model was used. The radiation intensity exponent varied from 0.3 to 0.6 possibly due to chain-length effects and pseudo-first order termination, respectively. The final degree of conversion increased with curing temperature (T_cure) and was correlated with the flexibility of the dimethacrylate. These data were fitted to a theoretical expression relating the final conversion to the resin T_g and to the T_cure. © 1993 John Wiley & Sons, Inc.     

Synthesis and rheological properties of polylactide/poly(ethylene glycol) multiblock copolymers

Ring-opening polymerization of D,L-lactide was carried out in the presence of poly(ethylene glycol), using Zn powder as catalyst. The hydroxyl-capped PLA-PEG-PLA triblock copolymers were coupled with adipoyl chloride at different molar ratios under mild conditions. N-Dimethylaminopyridine (DMAP) was used as catalyst of the coupling reaction. The resulting PLA/PEG multiblock copolymers were characterized by various analytical techniques such as IR, 1H NMR, SEC, and DSC. Sol-gel transition properties of the multiblock copolymers were investigated by mechanical rheology. The data showed that the sol-gel transition temperature and the transition modulus increased with increasing molecular weight and the solution concentration of the multiblock copolymers. [Graph: see text] Variation of storage modulus (G') and loss modulus (G') as a function of temperature for a 20% sample of MB3.     

Synthesis and properties of segmented block copolymers based on mixtures of poly(ethylene oxide) and poly(tetramethylene oxide) segments

The synthesis and characterisation of segmented block copolymers based on mixtures of hydrophilic poly(ethylene oxide) and hydrophobic poly(tetramethylene oxide) polyether segments and monodisperse crystallisable bisester tetra-amide segments are reported. The PEO length was varied from 600 to 8000 g/mol and the PTMO length was varied from 650 to 2900 g/mol. The influence of the polyether phase composition on the thermal mechanical and the elastic properties of the resulting copolymers was studied.The use of high melting monodisperse tetra-amide segments resulted in a fast and almost complete crystallisation of the rigid segment. The copolymers had only one polyether glass transition temperature, which suggests that the amorphous polyether segments were homogenously mixed. Thermal analysis of the copolymers showed one polyether melting temperature that was lower than in the case of ideal co-crystallisation between the two polyether segments. However, at PEO or PTMO lengths larger than 2000 g/mol two polyether melting temperatures were observed. The copolymer with the best low temperature properties was based on a mixture of PEO and PTMO segments, both having a molecular weight of 1000 g/mol, at a weight ratio of 30/70.     

Synthesis and characterization of poly(phenylacetylene)s carrying oligo(ethylene oxide) pendants

A group of new amphiphilic poly(phenylacetylene)s bearing polar oligo(ethylene oxide) pendants, poly{4‐[2‐(2‐hydroxyethoxy)ethoxy]phenylacetylene} ( 1 ), poly(4‐{2‐[2‐(2‐hydroxyethoxy)‐ethoxy]ethoxy}phenylacetylene) ( 2p ), poly(3‐{2‐[2‐(2‐hydroxyethoxy)ethoxy]ethoxy}phenylacetylene) ( 2m ), poly(4‐{2‐[2‐(2‐methanesulfonyloxyethoxy)ethoxy]ethoxy}phenylacetylene) ( 3 ), poly(4‐{2‐[2‐(p‐toluenesulfonyloxyethoxy)ethoxy]ethoxy}phenylacetylene) ( 4 ), poly(4‐{2‐[2‐(2‐trimethylsilyloxy‐ethoxy)ethoxy] ethoxy}phenylacetylene) ( 5 ), and poly(4‐{2‐[2‐(2‐chloroethoxy)ethoxy]ethoxy}phenylacetylene) ( 6 ), were synthesized with organorhodium complexes as the polymerization catalysts. The structures and properties of the polymers were characterized with IR, UV, NMR, and thermogravimetric analysis. 1 , 2p , and 2m , the three polymers containing pendants with hydroxyl groups, were oligomeric or insoluble. The organorhodium complexes worked well for the polymerization of the monomers without hydroxyl groups, giving soluble polymers 3 – 6 with a weight‐average molecular weight up to ～160 × 10³ and a yield up to 99%. Z‐rich polymers 3 – 6 could be prepared by judicious selections of the catalyst under optimal conditions. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1153–1167, 2006     

Kinetic comparison of isomeric oligo(ethylene oxide) (meth)acrylates: Aqueous polymerization of oligo(ethylene oxide) methyl ether methacrylate and methyl 2-(oligo(ethylene oxide) methyl ether)acrylate macromonomers

The photoinduced energy/electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerizations of oligo(ethylene oxide) monomethyl ether methacrylate (OEOMA, also known as poly[ethylene glycol] methyl ether methacrylate, PEGMA) and isomeric methyl 2-(oligo(ethylene oxide) methyl ether)acrylate (2OEOAM) macromonomers with OEO average degree of polymerization of 22 or 45 were conducted in aqueous media to provide insight into the effect of monomer structure on grafting-through RAFT of 1,1-disubstituted acrylic macromonomers. The polymerizations of all four monomers reached nearly quantitative conversion. The longer macromonomers polymerized faster than the shorter ones within the same monomer class. The OEO side chain at the α (i.e., 2-) position of isomeric acrylates significantly slowed RAFT polymerization in comparison with OEO ester side chain of methacrylates.     

Synthesis and properties of siloxane(ethylene oxide)urethane block copolymers

A new approach to the synthesis of hydrolytically stable dimethylsiloxane-ethylene oxide polyblock copolymers is described, in which ethylene oxide and siloxane blocks are linked by urethane groups. The molecular-mass parameters of block copolymers of different compositions are determined by capillary viscometry, light scattering, and gel-permeation chromatography. The temperature transitions in copolymers are characterized by differential scanning calorimetry.     

Hydrophilic segmented block copolymers based on poly(ethylene oxide) and monodisperse amide segments

Segmented block copolymers based on poly(ethylene oxide) (PEO) flexible segments and monodisperse crystallizable bisester tetra‐amide segments were made via a polycondensation reaction. The molecular weight of the PEO segments varied from 600 to 4600 g/mol and a bisester tetra‐amide segment (T6T6T) based on dimethyl terephthalate (T) and hexamethylenediamine (6) was used. The resulting copolymers were melt‐processable and transparent. The crystallinity of the copolymers was investigated by differential scanning calorimetry (DSC) and Fourier Transform infrared (FTIR). The thermal properties were studied by DSC, temperature modulated synchrotron small angle X‐ray scattering (SAXS), and dynamic mechanical analysis (DMA). The elastic properties were evaluated by compression set (CS) test. The crystallinity of the T6T6T segments in the copolymers was high (>84%) and the crystallization fast due to the use of monodisperse tetra‐amide segments. DMA experiments showed that the materials had a low T_g, a broad and almost temperature independent rubbery plateau and a sharp flow temperature. With increasing PEO length both the PEO melting temperature and the PEO crystallinity increased. When the PEO segment length was longer than 2000 g/mol the PEO melting temperature was above room temperature and this resulted in a higher modulus and in higher compression set values at room temperature. The properties of PEO‐T6T6T copolymers were compared with similar poly(propylene oxide) and poly(tetramethylene oxide) copolymers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4522–4535, 2007     

星形聚氧乙烯及星形杂臂氧化乙烯-苯乙烯共聚物的合成

以原子转移自由基偶联法合成了多臂星形聚合物S-PEO和星形杂臂共聚物PEO-PS。以傅立叶红外光谱(FT-IR)和核磁共振(1H NMR)分析方法确定了产物的结构。以GPC分析测试了产物的分子量和分子量分布。GPC分析结果表明所得聚合物分子量增大,分子量分布窄,偶联反应效率可高达99%以上。     

Characterization and demulsification of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers

Four poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers with different molecular weights and PPO/PEO composition ratios were synthesized. The characterization of the PEO-PPO-PEO triblock copolymers was studied by surface tension measurement, UV-vis spectra, and surface pressure method. These results clearly showed that the CMC of PEO-PPO-PEO was not a certain value but a concentration range, in contrast to classical surfactant, and two breaks around CMC were reflected in both surface tension isotherm curves and UV-vis absorption spectra. The range of CMC became wider with increasing PPO/PEO composition ratio. Surface pressure Pi-A curves revealed that the amphiphilic triblock copolymer PEO-PPO-PEO molecule was flexible at the air/water interface. We found that the minimum area per molecule at the air/water interface increased with the proportion of PEO chains. The copolymers with the same mass fractions of PEO had similar slopes in the isotherm of the Pi-A curve. From the demulsification experiments a conclusion had been drawn that the dehydration speed increased with decreased content of PEO, but the final dehydration rate of four demulsifiers was approximate. We determined that the coalescence of water drops resulted in the breaking of crude oil emulsions from the micrograph.     

Synthesis and characterization of anionic graft copolymers containing poly(ethylene oxide) grafts

Anionic graft copolymers were synthesized through grafting of poly(ethylene glycol) monomethyl ether (MPEG) onto terpolymers containing succicinic anhydride groups. The backbone polymers were prepared through radical terpolymerization of maleic anhydride, styrene, and one of the following monomers: methyl methacrylate, ethylhexyl methacrylate, and diethyl fumarate. MPEG of different molecular weights were grafted onto the backbone through reactions with the cyclic anhydride groups. In this reaction one carboxylic acid group is formed together with each ester bond. The molecular weights of MPEG were found to influence the rate of the grafting reaction and the final degree of conversion. The graft copolymers were characterized by IR, GPC, and ¹H-NMR. Thermal properties were examined by DSC. Graft copolymers containing 50% w/w of MPEG 2000 grafts were found to be almost completely amorphous, presumably because of crosslinking, and hydrogen bonding between carboxylic acid groups in the backbone and the ether oxygens in MPEG grafts. © 1995 John Wiley & Sons, Inc.     

Synthesis of oligo(ethylene glycol) toward 44-mer

A synthetic method for oligo(ethylene glycol) toward 44-mer (FW = 1956.35) is described. Reiteration of Williamson's ether synthesis and hydrogenation to remove protecting benzyl group affords desired oligo(ethylene glycol) toward 44-mer in moderate yields. The advantages in this method are use of commercially easily available materials as starting materials and procedures avoiding difficulty in purification of the products as much as possible.     

Synthesis of oligo(ethylene glycol) methacrylate polymer brushes

Here we report a study into controlling the polymerization of mono-hydroxy and mono-methoxy terminated oligo(ethylene glycol) methacrylates (HOEGMA and MeOEGMA, respectively) from functionalised, planar surfaces via atom transfer radical polymerization (ATRP). The effects of initiator structure, initiator density, temperature, and monomer ratios have been investigated for these polymerizations. The polymer brushes grown in this way were found to convey protein resistance to the underlying inorganic substrates, prone to facile protein adsorption in their native state.     

Synthesis and characterization of biodegradable aliphatic copolyesters with poly(ethylene oxide) soft segments

A series of multiblock poly(ether-ester)s based on poly(butylene succinate) (PBS) as the hard segments and hydrophilic poly(ethylene oxide) (PEO) as the soft segments was synthesized with the aim of developing degradable polymers which could combine the mechanical properties of high performance elastomers with those of flexible plastics. The aliphatic poly(ether-ester)s were synthesized by the catalyzed two-step transesterification reaction of dimethyl succinate, 1,4-butanediol and α,ω-hydroxyl terminated poly(ethylene oxide) (PEO, = 1000 g/mol) in bulk. The content of soft PEO segments in the polymer chains was varied from about 10 to 50 mass%. The effect of the introduction of the soft PEO segments on the structure, thermal and physical properties, as well as on the biodegradation properties was investigated. The composition and structure of these aliphatic segmented copolyesters were determined by ¹H NMR spectroscopy. The molecular weights of the polyesters were verified by gel permeation chromatography (GPC), as well as by viscometry of dilute solutions and polymer melts. The thermal properties were investigated using differential scanning calorimetry (DSC). The degree of crystallinity was determined by means of DSC and wide-angle X-ray scattering. A depression of melting temperature and a reduction of crystallinity of the hard segments with increasing content of PEO segments were observed. Biodegradation of the synthesized copolyesters, estimated in enzymatic degradation tests in phosphate buffer solution with Candida rugosa lipase at 37 °C was compared with hydrolytic degradation in the buffer solution. The weight losses of the samples were in the range from 2 to 10 mass%. GPC analysis confirmed that there were significant changes in molecular weight of copolyesters with higher content of PEO segments, up to 40% of initial values. This leads to conclusion that degradation mechanism of the poly(ether-ester)s based on PEO segments occurs through bulk degradation in addition to surface erosion.     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

Li+ transport in lithium sulfonylimide-oligo(ethylene oxide) ionic liquids and oligo(ethylene oxide) doped with LiTFSI

The Li+ environment and transport in an ionic liquid (IL) comprised of Li+ and an anion of bis(trifluoromethanesulfonyl)imide anion (TFSI-) tethered to oligoethylene oxide (EO) (EO(12)TFSI-/Li+) were determined and compared to those in a binary solution of the oligoethylene oxide with LiTFSI salt (EO(12)/LiTFSI) by using molecular dynamics (MD) simulations and AC conductivity measurements. The latter revealed that the AC conductivity is 1 to 2 orders of magnitude less in the IL compared to the oligoether/salt binary electrolyte with greater differences being observed at lower temperatures. The conductivity of these electrolytes was accurately predicted by MD simulations, which were used in conjunction with a microscopic model to determine mechanisms of Li+ transport. It was discerned that structure-diffusion of the Li+ cation in the binary electrolyte (EO(12)/LiTFSI-) was similar to that in EO(12)TFSI-/Li+ IL at high temperature (>363 K), thus, one can estimate conductivity of IL at this temperature range if one knows the structure-diffusion of Li+ in the binary electrolyte. However, the rate of structure-diffusion of Li+ in IL was found to slow more dramatically with decreasing temperature than in the binary electrolyte. Lithium motion together with EO(12) solvent accounted for 90% of Li+ transport in EO(12)/LiTFSI-, while the Li+ motion together with the EO(12)TFSI- anion contributed approximately half to the total Li+ transport but did not contribute to the charge transport in IL.     

Poly[(methylene oxide) oligo(ethylene oxide)] vs. poly(ethylene oxide) as hosts for neodymium compounds

In view of the residual crystallinity in PEO found to limit the solubility of some Nd³⁺-compounds, amorphous PEO (aPEO) was synthesized for exploration as an alternative host. Complexation, solubility limit, morphology, and response to moisture absorption in the doped systems were investigated using FTIR, DSC, TGA, and WAXD techniques. Representing a perturbation to the structural regularity present in PEO, aPEO was found to present lower solubilities for dopants (Nd(act)₃ and Nd(acac)₃, both characterized by a weak Nd³⁺–ether oxygen interaction. On the other hand, no difference in solubility was observed for dopant Nd(NO₃)₃, characterized by a strong Nd³⁺–ether oxygen interaction. Laser interferometry was employed to assess film homogeneity of the Nd(NO₃)₃-doped systems across a 20-mm diameter, and the measured peak-to-valley distortion values were observed to be encouraging for practical applications. © 1994 John Wiley & Sons, Inc.     

Synthesis and dynamic mechanical properties of cross-linked multiblock poly(urethane-imide) copolymers

Russian Chemical Bulletin - Poly(urethane-imide) copolymers (PUICs) containing reactive carboxyl groups in hard imide segment were synthesized from poly(propylene glycol) with isocyanate end...