Random Copolyether Research Articles

Correlation among copolyether spacers, molecular geometry and interfacial properties of extended surfactants

Extended surfactants (e-surfactants) generally occupy larger surface adsorption areas and display better properties than conventional surfactants, which is attributed to propoxy-containing polyether spacers coiled more and collapsed more on various interfaces but lack of firm evidences. In this work, the target products of sodium dodecyl poly(propoxy-ethoxy) sulfates are synthesized on the basis of designing copolyether spacers by both diblock and random copolymerization mechanisms. A unique insoluble monolayer experiment is proposed to estimate surface spreading areas of the copolyether intermediates. Moreover, the correlation between copolyether spacers and molecular geometry and interfacial properties of the e-surfactants is investigated. We find that surface spreading areas of the copolyether intermediates are much larger than that of the dodecanol precursor and slightly larger than and positively correlated with surface adsorption areas of the corresponding target e-surfactants, which provides a direct evidence for biphasic affinity of the copolyether spacers to drive the spacers three-dimensionally extended on various interfaces and make e-surfactants becoming rugby ball shapes. Furthermore, it is shown that the more random copolyether spacer, the larger molecular area on the surface the e-surfactant occupies, being responsible for many unique interfacial properties of e-surfactants.

Influence of Temperature on Mechanical Properties of P(BAMO-r-THF) Elastomer.

The relationship between temperature and the mechanical properties of an end cross-linked equal molar random copolyether elastomer of 3,3-bis(azidomethyl)oxetane and tetrahydrofuran (P(BAMO-r-THF)) was investigated. During this investigation, the performances of two P(BAMO-r-THF) elastomers with different thermal histories were compared at different temperatures. The elastomer as prepared at 20 °C (denoted as S0) exhibited semi-crystallization morphology. Wide angle X-ray diffraction analysis indicated that the crystal grains within elastomer S0 result from the crystallization of BAMO micro-blocks embedded in P(BAMO-r-THF) polymeric chains, and the crystallinity is temperature irreversible under static conditions. After undergoing a heating-cooling cycle, this elastomer became an amorphous elastomer (denoted as S1). Regarding mechanical properties, at 20 °C, break strains and stresses of 315 ± 22% and 0.46 ± 0.01 MPa were obtained for elastomer S0; corresponding values of 294 ± 6% and 0.32 ± 0.02 MPa were obtained for elastomer S1. At −40 °C, these strains and stresses simultaneously increased to 1085 ± 21% and 8.90 ± 0.72 MPa (S0) and 1181 ± 25% and 10.23 ± 0.44 MPa (S1), respectively, owing to the strain-induced crystallization of BAMO micro-blocks within the P(BAMO-r-THF) polymeric chains.

Anionic ring-opening copolymerization of styrene oxide with monosubstituted oxiranes: analysis of composition of prepared new copolyether-diols by MALDI-TOF mass spectrometry

Several new random copolyethers of styrene oxide (SO) and other monosubstituted oxirane as comonomer, i.e., propylene oxide (PO), isopropyl glycidyl ether (IPGE) or allyl glycidyl ether (AGE), were synthesized in THF solution at room temperature. As initiator monopotassium salt of dipropylene glycol activated by 18-crown-6 complexing agent was used. Synthesized copolyether-diols were characterized by SEC, 13C NMR and MALDI-TOF techniques. They were unimodal and had Mn = 3500–4600 and relatively low dispersity (Mw/Mn = 1.16–1.18). Low unsaturation of the products resulted from chain transfer reaction to styrene oxide. Composition of SO/PO-diol, SO/IPGE-diol and SO/AGE-diol copolymers was determined by MALDI-TOF mass spectrometry. Homopolymers were not formed during the processes.Graphical abstract

Thermal and mechanical properties of two kinds of hydroxyl-terminated polyether prepolymers and the corresponding polyurethane elastomers

In order to analyze the differences in performance between two kinds of hydroxyl-terminated polyether (HTPE) binders, the curing reaction kinetics of the prepolymers and polyfunctional isocyanate (N-100) molecules and the thermal properties of the prepolymers and the corresponding polyurethane (PU) elastomers were studied by non-isothermal differential scanning calorimetry. The mechanical properties of PU elastomers were also studied by uniaxial tensile tests. With these data, the binder type could be chosen more appropriately for its application in rocket propellant formulations. The results showed that the reactivity of hydroxyl-terminated block copolyether (TPEG) with an isocyanate group is higher than that of hydroxyl-terminated random copolyether (PET). The chain flexibility of TPEG was less than that of PET, but the stereoregularity and crystallization ability of the former were superior. Compared to the prepolymers, the chain flexibility of the corresponding PU elastomers was reduced, and the crystallization ability became weaker such that their onset of crystallization was delayed. After the prepolymers were reacted with N-100, the thermal properties of PU elastomers remained consistent with their respective prepolymers. In summary, it was concluded that the mechanical properties of TPEG/N-100 PU elastomer films were found to be superior to the PET/N-100 films.

Effect of Hydroxyl-Terminated Random Copolyether (PET) and Hydroxyl-Terminated Polybutadiene (HTPB) on Thermal Decomposition Characteristics of Ammonium Perchlorate

The effects of two binders (PET and HTPB) on thermal decomposition characteristics of Ammonium Perchlorate were studied by TG-FTIR, DSC and SEM. When Hydroxyl-terminated polybutadiene (HTPB) mixes with AP, there is no obvious mutual effect in the process of heating, but it happen in the other way when Hydroxyl-terminated random copolyether (PET) mixes with AP. During the heating process of PET-AP mixture, the decomposition of PET occur in advance significantly, so that the porous structure of AP at the low-temperature decomposition stage becomes more significant, the total amount of heat released increases significantly, and the weight-loss ratio of AP about the two stages increases to about 2:1. During the thermal decomposition, the heat release and N2O gas production of PET-AP mixture is milder than the HTPB-AP, which is more conducive to the insensitive properties of propellant.

Tribological properties of aqueous solutions with lauric acid random copolyether (LPE) added

This work presents the results of tribological investigations of lubricating substances composed of water and a nonionic surfactant: lauric acid random copolyether (LPE), as additive. At the current stage of investigation, aqueous solutions with LPE additives are prepared and subsequently the lowering friction and reducing wear behaviors are tested by means of friction/wear tester, in conjunction with that the film forming properties experiments are carried out with a nanoscale film thickness measure apparatus. The contact is under condition of steel-steel tribo-pair. The results show that the coefficient of friction measured decreases considerably to about over 60% relative to water. The film thickness data of friction process lubricated by aqueous solutions with LPE added show that the lubrication is in boundary lubrication regime. The results indicate that aqueous solutions with LPE added can be used to improve the lubricity and they may be applied to real tribological systems.

Synthesis of Double Alkyl EO/PO Random Copolyethers with KOH Catalyst

Ethylene oxide (EO) and propylene oxide (PO) random copolymer was synthesized with 1,2-propanediol as initiator, then the end-capping process was carried out by adding various alkyl halides and potassium hydroxide (KOH) to produce the double alkyl EO/PO random copolyethers. The factors effecting alkyl-capping rate were discussed. The results showed that when the molar ratio of hydroxyl group/KOH/1-bromobutane was 1/1.9/1.9, reacting time 6.5 hr and reacting temperature 50°C, the alkyl-capping rate could reach over 80%. The end-capping rate would also increase with the increasing content of ethylene oxide in the random polyether, and the end-capping rate of the EO/PO/EO block-polyether was high than that of the random polyether with same molecular weight. Instead of 1-bromobutane, ethyl bromide promised a higher whereas chloralkane gave a lower end-capping rate respectively.

Study on Friction-reducing and Anti-wear Performances of Lauric Acid Random Copolyether Aqueous Solutions

Lauric acid random copolyether(LPE) aqueou solutions with different mass fraction are prepared.Friction-reducing and anti-wear performances of LPE aqueous solutions are tested on the friction and wear tester.Tribo pairs of steel/aluminum and steel/steel are selected and the influences of mass fraction,load,and specimen surface roughness are discussed.The surface morphology of samples are measured by the phase shift MicroXAM-3D and the energy dispersive spectrometer.The results show that friction-reducing capability of 0.5% LPE aqueous solutions decrease up to 65% or more,being compared to water.As the mass fraction,load and specimen surface roughness increasing,friction-reducing performances get better.The specimen wear scars are shallow and uniform.The phenomenon indicates that polarity adsorption groups in LPE aqueous solutions forming thick chemical adsorbed film and physical adsorbed film on the metal surfaces.The films have better friction-reducing and anti-wear performances by seperating friction surfaces.The polar molecule has saturated adsorption capacity,so it shows good friction-reducing and anti-wear properties at low mass fraction.It lays a foundation for the rosy prospect in industrial application.

Mesoglobules of random copolyethers as templates for nanoparticles

AbstractAn approach to nanoparticles based upon the thermosensitivity of a copolyether is described. Two thermosensitive copolymers of glycidol with molar masses of 800,000 g/mol randomly substituted with ethyl isocyanate (28 and 35% substitution) were used to obtain mesoglobules. The effects of copolymer concentration and of the presence of surfactants (sodium dodecyl sulfate and hexadecyltrimethylammonium bromide) on the size of the mesoglobules formed were investigated. The obtained mesoglobules were monomodal and of narrowly distributed diameters, as shown by dynamic light scattering and atomic force microscopy measurements. The radical nucleated copolymerization of N‐isopropylacrylamide with N,N′‐methylenebisacrylamide as a crosslinker was performed in the presence of the mesoglobules. Nanoparticles of monomodal size distribution and low dispersity were obtained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4074–4083, 2010

Synthesis and characterization of thermoplastic polyurethanes as binder for novel thermoplastic propellant

AbstractTwo series of thermoplastic polyurethanes (TPUs), which used nitroester plasticiable tetrahydrofuran‐ethylene oxide random copolyether as soft segment and adduction products of isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) with 1,4‐butanediol as hard segments respectively, were successfully synthesized as binders for novel thermoplastic propellant. Mechanical tests and DSC techniques were applied to make characterizations of the polymers in order to choose candidate materials. Results shown that the TPU based on IPDI with fraction of the hard segment around 45% will meet requirements of propellant in terms of mechanical properties and glass transition of the soft segment phase. The results were further manifested in detail by quantitative studies of the degree of microphase separation as well as hydrogen bonding within the hard segment domain based on the equations established through FTIR and DSC analyses. It was found that mixing of two phases, which mainly referred to the mount of the hard segment dissolving into the soft segment phase, was as little as 10% in IPDI series TPUs, whereas it was almost up to 30% in TDI series. This indicated that better phase separation was achieved in IPDI series TPU. By contrast, studies of hydrogen bonding in domain revealed that the domain of TPUs prepared with TDI was much oriented in comparison with that with IPDI, which indicated higher processing temperatures. The results were raised by the melting index results under required conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2961–2966, 2002; DOI 10.1002/app.2324

Molecular orientation in quenched channel flow of a flow aligning main chain thermotropic liquid crystalline polymer

We report measurements of molecular orientation in solid specimens of a main-chain thermotropic liquid crystalline polymer (LCP) that were quenched from mixed shear-extensional channel flows. The polymer under investigation is a random copolyether with mesogens separated by flexible hydrocarbon spacers. This polymer is known to exhibit ‘flow aligning’ dynamics under slow shear flow. Experiments were designed to preserve the molecular orientation state, representative of steady, isothermal channel flow in the solid samples, so that comparisons could be made against in situ channel flow measurements on other main chain thermotropes without flexible spacers, including a commercial fully aromatic copolyster. In the flow aligning material, little change in orientation was found in slit-contraction flows, and only modest drops in orientation were found in slit-expansion flow. This contrasts strongly with data on commercial LCPs, suggesting that these materials may be of the ‘tumbling’ type.

Synthesis and Matrix-Assisted Laser Desorption Ionization−Time of Flight Characterization of an Exactly Alternating Copolycarbonate and Two Random Copolyethers Containing Schiff Base Copper(II) Complex Nonlinear Optical Units in the Main Chain

Copolymers containing second-order nonlinear optical (NLO) active transition metal complexes into the main chain were synthesized and characterized by matrix-assisted laser desorption ionization−time of flight mass spectrometry (MALDI−TOF MS), TG, and DSC analyses for the first time. The Cu(II) complex Ia of the N,N‘-bis(2,4-dihydroxybenzylidene)-1,2-phenylenediamine ligand was synthesized and used as the NLO unit. The polycondensation between the copper(II) complex Ia (NLO unit) and butanediol bischloroformate was performed to obtain the exactly alternating copolycarbonate II. Two copolyethers, III and IV, containing different amounts of NLO units in the main chain (10% and 47%, respectively), were obtained by reaction of dibromomethane and suitable mixtures of the Cu(II) diimine complex Ia and bisphenol A in different molar ratios. The resulting copolymers II−IV were characterized by MALDI−TOF MS. The structure of low molecular weight oligomers contained in each polymeric sample inferred by MALDI spectr...

Microphase separation behaviour in a series of thermotropic liquid crystalline copolyethers

The phase transition and microphase separation behaviour have been studied by means of differential scanning calorimetry, polarizing microscopy, depolarizing transmittance and X-ray diffraction measurements for a series of thermotropic liquid crystalline random copolyethers. These are composed of two similar aromatic azomethine ether units, derived from 3,3′-dimethoxy-4,4′-diformyl-α,ω-diphenoxyhexane with 4,4′-diaminodiphenylmethane (system A) and with 4,4′-phenylenediamine (system B). These copolymers, with the exception of those containing a high content of the A component, were found to transform from a crystalline to a nematic liquid crystalline, and finally to an isotropic phase. For the specimens with 40, 50 and 60 mol% of the A component a microphase separation phenomenon was distinctly observed: segments of the A and B components along the polymer backbones may separately form their own crystalline domains, which melt in different temperature ranges. After this, the A domains are transformed directly into the isotropic state, while the B segments can still form special mesomorphic domains. A phase diagram for these copolymers was also obtained: the melting points of the crystalline domains formed by segments of the A component were found to be only slightly changed with variation in the component content, while the melting and the isotropization transition temperatures of the B component domains were lowered significantly with decreases in the B component content.

Functional polymers and sequential copolymers by phase transfer catalysis. 24. The influence of molecular weight on the thermotropic properties of a random copolyether based on 1,5‐dibromopentane, 1,7‐dibromoheptane, and 4,4′‐dihydroxy‐α‐methylstilbene

AbstractThe influence of molecular weight on thermal transitions and on their thermodynamic parameters is discussed for a random thermotropic liquid crystalline copolyether based on the reaction of a 1:1 molar mixture of 1,5‐dibromopentane and 1,7‐dibromoheptane with 4,4′‐dihydroxy‐α‐methylstilbene. Optimum phase transfer catalyzed polyetherification reaction conditions were established for the synthesis of polymers containing bromoalkane chain ends only over a wide variety of molecular weights. All these copolyethers present a crystalline and an enantiotropic nematic mesophase over the entire range of molecular weights studied. Both the thermal transitions and their thermodynamic parameters are strongly molecular weight‐dependent up to Mn = 10,000–12,000, after which they remain constant. The enthalpies and entropies of isotropization of the copolyethers are higher than those of melting. This is in contrast to the same thermodynamic parameters of the corresponding homopolyethers. The enthalpies and entropies of isotropization of both homopolymers and copolymers present similar values, suggesting that copolymerization does decrease the degree of order in the crystalline phase but does not significantly change the alignment degree of the mesogenic units in the nematic mesophase.

Functional polymers and sequential copolymers by phase transfer catalysis. 25. Transformation of a monotropic mesophase into an enantiotropic one by increasing the molecular weight of the polymer and by copolymerization

AbstractThe influence of molecular weight on thermal transitions and on the thermodynamic parameters was studied for two polymers based on 4,4′‐dihydroxy‐α‐methylstilbene with either 1,9‐dibromononane (HMS‐C9 polyethers) or 1,11‐dibromoundecane (HMS‐C11 polyethers). HMS‐C9 polyethers present an enantiotropic nematic mesophase over the entire range of molecular weights and a monotropic smectic mesophase for polymers of number average molecular weights higher than 17,000. The low molecular weight HMS‐C11 polyethers are only crystalline. On increasing their molecular weight, the polymers become monotropic nematics, and at higher molecular weights, enantiotropic nematics. Up to a composition containing as little as 20 mol % nonane structural units, the random copolyethers based on 1,9‐dibromononane, 1,11‐dibromoundecane, and 4,4′‐dihydroxy‐α‐methylstilbene (HMS‐C9/11 copolyethers) exhibit on cooling a phase diagram resembling that of HMS‐C9 polyether. HMS‐C9/11 containing about a 1/1 mole ratio between the two spacers presents both smectic and nematic enantiotropic mesophases. These results suggest that the phase diagram of random liquid crystalline copolymers is controlled by the shorter spacer. The thermodynamic parameters of isotropization for both polyethers and copolyethers are compared and suggest that copolymerization does not significantly decrease the degree of order of the mesogenic units in the mesomorphic phase.

Functional polymers and sequential copolymers by phase‐transfer catalysis. 16. Influence of sequence distribution on the mesomorphic properties of thermotropic copolyethers containing 4,4′‐dihydroxybiphenyl

AbstractRandom and alternating thermotropic liquid‐crystalline copolyethers have been synthesized from 4,4′‐dihydroxybiphenyl and a 1/1 mol ratio of 1,5‐dibromopentane and α,ω‐dibromoalkanes by a two‐phase (organic solvent‐aqueous NaOH) phase‐transfer‐catalyzed polyetherification. Random copolyethers were prepared from α,ω‐dibromoalkanes having six to twelve methylene units. Their phase behavior was compared with those of the perfectly alternating copolyethers containing five methylene units in one spacer and eight, nine, or eleven methylene units in the other, respectively. An odd‐even dependence in thermal transitions has been observed in both oligomeric systems. In all cases, alternating copolyethers, even though comparatively lower in molecular weight, have given rise to higher melting and isotropization temperatures. Since the increase in the melting temperature is larger than the increase in the isotropization temperature, the thermal stability range of the mesophase has narrowed for alternating copolyethers with respect to their random copolyether counterparts.