Random Copoly Research Articles

Enhanced electrorheological effectiveness and temperature effect of suspensions based on poly(ionic liquid)s neutralized with mixed counterions

A series of random co-poly(ionic liquid)s (co-PILs) neutralized with mixed counterions of organic bis(trifluoromethane sulfonyl)imide ([TFSI]) and inorganic tetrafluoroborate ([BF 4 ]) of different mole ratio had been synthesized for use as electrorheological (ER) particles. The temperature-modulated ER effect of the co-PIL particles had been investigated and compared with that of homo-poly(ionic liquid)s neutralized with single organic [TFSI] counteranions. This work demonstrated that the ER effectiveness and temperature effect of electrorheological fluid based on neat organic counteranions-typed PILs can be significantly improved by a simple substitution of inorganic counteranions with a suitable mole ratio. The higher electrorheological effectiveness with suppressed leakage current density and enhanced temperature stability originated from that the substitution of inorganic counteranions for organic counteranions could systematically elevate the glass transition temperature and modulate the activation energy of ion movement in PILs matrix. Linear polymeric ionic liquids (PILs) neutralized with mixed counteranions of organic ([TFSI]) and inorganic ([BF 4 ]) could exhibit higher ER effectiveness and broader working temperatures range than the analogous PILs neutralized with single organic counteranions. • PILs containing organic and inorganic counterions of various mole ratio was prepared for use as electrorheological particles. • Partial replacement of [TFSI] by [BF 4 ] could improve the electrorheological effectiveness and thermal stability of PILs. • Partial replacement of [TFSI] by [BF 4 ] could modulate the glass temperature and ionic shifting activation energy of PILs.

Post-polymerization modifiable aromatic (co)poly(ether sulfone)s possessing pendant norbornenyl groups based upon a new bisphenol

A new bisphenol possessing pendant norbornenyl group viz., 4, 4′-(bicyclo (2.2.1) hept-5-en-2 yl methylene) bis (2-methoxyphenol) (BPA-NB) was synthesized by a single-step base-catalyzed condensation reaction of 5-norbornene-2-carboxaldehyde with guaiacol. NMR spectral data indicated formation of BPA-NB comprising of isomeric components. A series of (co)poly(ether sulfone)s possessing pendant norbornenyl groups was synthesized by nucleophilic aromatic substitution polycondensation of varying molar ratio of BPA-NB and bisphenol-A (BPA) with bis(4-fluorophenyl) sulfone. Inherent viscosity values and number average molecular weights of (co)poly(ether sulfone)s were in the range 0.67–1.01 dL/g and 75,400–1,16,300 g/mol, respectively indicating the formation of reasonably high molecular weight polymers. Tough, transparent, and flexible films could be cast from chloroform solutions of these (co)poly(ether sulfone)s. (Co)poly(ether sulfone)s were characterized using FT-IR, 1H NMR and 13C NMR spectroscopy, XRD, TGA and DSC analysis. The formation of random copoly(ether sulfone)s was demonstrated by 13C NMR analysis. The incorporation of BPA-NB into (co)poly(ether sulfone)s resulted into improvement in Tg values. BPA-NB-based (co)poly(ether sulfone)s offered possibilities for post-modifications involving either methoxyl or norbornenyl groups. A representative copoly(ether sulfone) (PSU-NB-2) possessing pendant norbornenyl groups was chemically modified via thiol-ene reaction with three representative thiol compounds, namely, 1-dodecanethiol, 2-furanmethanethiol and 2-mercaptoethanol to yield corresponding post-modified polymers in a quantitative manner. Additionally, it was demonstrated that copoly(ether sulfone) possessing pendant norbornenyl groups could be used to form insoluble cross-linked gel in the presence of a multifunctional thiol cross-linker.

Aggregation of Cationic Amphiphilic Block and Random Copoly(vinyl ether)s with Antimicrobial Activity.

In this study, we investigated the aggregation behaviors of amphiphilic poly(vinyl ether)s with antimicrobial activity. We synthesized a di-block poly(vinyl ether), B3826, composed of cationic primary amine and hydrophobic isobutyl (iBu) side chains, which previously showed antimicrobial activity against Escherichia coli. B3826 showed similar uptake behaviors as those for a hydrophobic fluorescent dye, 1,6-diphenyl-1,3,5-hexatriene, to counterpart polymers including homopolymer H44 and random copolymer R4025, indicating that the iBu block does not form strong hydrophobic domains. The cryo-TEM observations also indicated that the polymer aggregate of B3826 appears to have low-density polymer chains without any defined microscopic structures. We speculate that B3826 formed large aggregates by liquid-liquid separation due to the weak association of polymer chains. The fluorescence microscopy images showed that B3826 bonds to E. coli cell surfaces, and these bacterial cells were stained by propidium iodide, indicating that the cell membranes were significantly damaged. The results suggest that block copolymers may provide a new platform to design and develop antimicrobial materials that can utilize assembled structures and properties.

Conformation Shift Switches the Chiral Amplification of Helical Copoly(phenylacetylene)s from Abnormal to Normal “Sergeants-and-Soldiers” Effect

Optically active helical random copoly(phenylacetylene)s were prepared from structurally similar monomers, (+)-3-hexadecylcarbamoyl-5-[((S)-1-phenylethyl)carbamoyl]phenylacetylene and 3-hexadecylcarbamoyl-5-(benzylcarbamoyl)phenylacetylene, under the catalysis of Rh[C(C6H5)═C(C6H5)2](nbd)(4-FC6H4)3P (nbd = 2,5-norbornadiene). The chiral amplification followed either normal or abnormal “sergeants-and-soldiers” rule depending on the solvent nature. In apolar solvents (i.e., CHCl3 and THF), contracted cis-cisoid M- and P-helices were selectively induced for the copolymers containing chiral units below or above 74 mol %, respectively. In polar solvent (i.e., CHCl3/CH3OH, 70/30, v/v), a cis-cisoid to cis-transoid transition occurred and stretched M-helices were dominantly formed, the optical activity of which scaled up nonlinearly with increasing chiral component. This unusual phenomenon was rationalized by the distinct competing interactions between the vicinal chiral/achiral and chiral/chiral unit pairs in t...

Single-Ion Block and Random Copoly(ionic liquid)s As Innovative Electrolytes for All-Solid State Li Batteries

In recent years, wide research efforts have been devoted to the development of solid polymer electrolytes (SPEs) with the goal to enhance the intrinsic safety and replace the traditional flammable liquid electrolytes employed in the lithium-ion battery technology (LIBs). Among SPEs, a new class of polyelectrolytes, namely poly(ionic liquid)s (PILs) has deserved considerable attention. Although significant progress has already been achieved with cationic PILs/Li salt composites, the power delivery of such electrolytes is hampered by the strong concentration gradients formed during battery operation. As an alternative the anionic polyelectrolytes or so called “polymeric single-ion conductors” have been recently suggested. In this work, we present two approaches for the preparation of the innovative families of single-ion polymer electrolytes. First approach consists in the synthesis of ionic block copolymers via RAFT polymerization technique. Such copolymers comprise poly(lithium 1-[3-(methacryloyloxy)propylsulfonyl]-1-(trifluoromethylsulfonyl)imide) and poly(ethylene glycol) methyl ether methacrylate blocks (Fig. 1A). This method allowed to vary the molecular weight of PILs and to gain the desired control over polymer’s T g and ionic conductivity. The “best” obtained polyelectrolyte with Mn = 2.5x104 g/mol shows the T g as low as -61 ºC, ionic conductivity as high as 2.3×10-6 and 1.2×10-5 S cm-1 at 25 and 60o C, respectively, wide electrochemical stability (4.5 V vs Li+/Li) and a lithium-ion transference number close to unity (0.83).Second utilized approach involves the free radical copolymerization of ionic liquid like monomers with poly(ethylene glycol) methyl ether methacrylate for the preparation of random ionic copolymers. Here, polymer’s ionic conductivity and T g were controlled by the nature of ionic monomer and the molar composition of statistic copolymer (Fig. 1B). The “optimal” coPIL with Mw = 4.2x105 g/mol demonstrates T g = -56 ºC, ionic conductivity equal to 1.8×10-6 and 1.5×10-5 S cm-1 at 25 and 60o C, respectively, wide electrochemical stability (4.2 V vs Li+/Li) and high lithium-ion transference number (0.91). Owing to the combination of all mentioned properties, the prepared polymer materials were used as solid polyelectrolytes as well as binders in the elaboration of truly solid Li/coPIL/LiFePO4 battery prototypes working at 60-70oC and delivering large capacities (up to 130 mAh/g), with an impressive charge/discharge efficiency and the capability to reversibly operate at relatively high rates up to C/5 (Fig. 1C). This work was supported by the Russian Foundation for Basic Research (projects no. 14-29-04039_ofi_m and 16-03-00768_a) and by European Commission (project no. 318873 «IONRUN»). J.R.N. gratefully acknowledges financial support from MARS-EV project (FP7/2007-2013, under grant agreement n° 609201). Figure 1

Development of functional electrospun fiber mats for potential wound healing and blood conservation

Event Abstract Back to Event Development of functional electrospun fiber mats for potential wound healing and blood conservation Xiaoqiang Yang1, 2, Jayachandran Kizhakkedathu1, 2 and Donald Brooks1, 2, 3 1 University of British Columbia, Centre for Blood Research, Canada 2 University of British Columbia, Department of Pathology & Laboratory Medicine, Canada 3 University of British Columbia, Department of Chemistry, Canada Introduction: Our aim is to develop and evaluate a novel tissue sealant utilizing the universal adhesion reaction based on multivalent interactions between phosphatidyl choline (PC) lipid head groups on cell membranes and synthetic choline phosphate (CP)–containing polymers[1]. Such polymers when electrospun into pads should both adhere to solid tissue and bind red blood cells (RBCs) and platelets to arrest bleeding at sites of tissue damage or surgery where vascular integrity is breached. These polymer webs should meet the mechanical and functional requirements for wound healing and blood conservation applications[2]-[5]. Materials and Methods: A nano scale fiber web consisting of a random copolymer containing the backbone of ε-caprolactone and its derivative with a pendent hydrophilic segment bearing functional CP groups was prepared by the electrospinning process. To achieve the copolymer, a new cyclic ester, γ-(2-bromo-2-methly propionyl)-ε-caprolactone, containing a pendent-activated alkyl bromide functional group was prepared[6]. This new monomer serves as both a monomer for ring-opening polymerization (ROP) with ε-caprolacone as well as an initiator for controlled atom transfer radical polymerization (ATRP). The random co-poly(caprolactone) via ROP was tuned to make a suitable candidate for the electrospin process, balancing hydrophobicity, hydrophilicity and the density of functional groups by adjusting the ratio of new monomer and ε-caprolactone. The synthesis of poly(ε-caprolactone)-graft- poly(2-(2-(2-(2-azidoethoxy) -ethoxy)ethoxy)ethyl methacrylate) was via a grafting-from technique, where poly(caprolactone) with pendent isobutyryl bromide groups acted as macroinitiator to initiate the ATRP azido monomer to yield the grafted copolymer containing a backbone of poly(caprolactone) and dispersed side chains of poly(methacrylate) with multiple azido groups. Finally, pre-prepared prop-2-ynyle phosphatidylcholine (CP monomer) was clicked onto the above grafted copolymer via the reaction between the pendent azido groups of the copolymer and the alkyne group of CP monomer. The CP monomer (prop-2-ynyle phosphatidylcholine) was prepared following our previously reported method[1]. The designed copolymers were characterized with NMR and FTIR to determine the MW and presence of functional groups and the electrospun web with SEM. Results and Discussion: Human RBCs incubated with the CP web formed a uniform layer on the mat surface attributed to multivalent interactions between CP groups on the web and PC groups on the cell membrane, demonstrating the material’s potential for blood conservation and sealing. Incubation in isotonic whole blood with reduced ionic strength resulted in enhanced adhesion and supports an electrostatic mechanism for the CP-PC association. Conclusion: We anticipate that this functional fiber mat will prove to be a fundamentally new and effective biomaterial for wound dressing and blood conservation practice.

Reactive melt mixing of PC/PEN blend. Structural characterization of reaction products

Chemical reactions occurring during reactive melt mixing of equimolar blend of poly(bisphenol-A carbonate) and poly(ethylene 2,6-naphthalate) at 280 °C in presence of a catalyst, were studied. Beside expected direct “inner–inner” ester-carbonate and outer–inner exchange reactions, consecutive reactions that lead to the elimination of CO2 and ethylene carbonate from backbone, were also detected. The composition and the architecture of the formed copolymers change as the mixing time increases. Initial PC-PEN block copolymers formed at lower mixing time (2 min) evolve towards the formation of naphthalate based random copoly(ester-ether)s at reaction time higher than 45 min, owing to total elimination of carbonate units. Determination of composition and microstructure of copolymers formed was attempted by (1H and 13C)-NMR analyses applying appropriate chemical microstructural model. Dyads and triads sequences determined here give detailed information on the change in the molar fractions of the sequences with increasing the reaction time. DSC analysis shows that block copolymer formed at 2 min mixing present two glass transition (Tg) temperatures close to those of initial homopolymers, whereas the other ones show a single Tg that changes as a function of their dyads molar compositions. Thermogravimetric analysis show that the more thermally stable copolymers are random copoly(ester-ether)s formed at higher reaction time.

Investigation on cyclization process of co-polyimides containing 2-(4-aminophenyl)-5-aminobenzimidazole units

As one type of high-performance polymers, polyimides have been extensively used in various fields. The cyclization reaction plays a significant role in the change of the polymeric chemical structure and physical properties. In this work, a series of random co-poly(amic acid)s (PAAs) were synthesized by introducing an aromatic heterocyclic diamine monomer (2-(4-aminophenyl)-5-aminobenzimidazole (BIA)) into the homopolyimide backbones of pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). Fourier transform infrared (FTIR) spectroscopy was employed to study the cyclization kinetics in the temperature range of 180–300°C. The results indicate that the addition of BIA decreases the cyclization rates, which is mainly attributed to the rigid-rod structure of the BIA. The mechanism of thermal imidization of the solid state co-PAA was also studied by FTIR using two-dimensional correlation spectroscopy method. The signs of the cross peaks in asynchronous spectra suggested that the imide-related modes changed prior to the amide mode, which indicates that cyclization occurred before the amide proton was abstracted. The result illustrates the truth that the introduction of BIA units into PMDA-ODA segments obviously increases the barrier for the meta-segment of PAA into corresponding polyimide, which is the essential reason for the decreasing cyclization rate.

Properties, morphology and structure of BPDA/PPD/ODA polyimide fibres

A family of random co-poly(amic acid)s containing 4,4′-oxydianiline (ODA) moiety were synthesised in N,N′-dimethylacetamide. The co-poly(amic acid) solutions were used as spinning dope for dry jet wet spinning process into as spun poly(amic acid) (PAA) fibres. The polyimide (PI) fibres were obtained from PAA fibres after being imidised and drawn in furnace. The processability and mechanical properties of the fibres were notably improved by incorporating ODA into 3,3′,4,4′-biphenyltetracarboxylic dianhydride/p-phenylenediamine (BPDA/PPD) backbone. The best strength and modulus of BPDA/PPD/ODA PI fibre (diamine mole ratio of PPD/ODA = 85∶15) attained 2·25 and 96·5 GPa respectively, which were approximately three times the tenacity of the BPDA/PPD PI fibre. The SEM image showed that the cross-section of each stage fibres was round and void free. In addition, ‘skin–core’ and microfibrillar structure were not observed. The thermal properties of PI fibres were also investigated. The results showed that the PI fibres have excellent thermal stability; moreover, the dimensional stability and structural homogeneity of the fibres were significantly improved by heat drawn stage. Tg was found to be ∼290°C by thermomechanical and dynamic mechanical analyses. The X-ray (wide angle X-ray diffraction and small angle X-ray scattering) experiments indicated that the ordering degree of longitudinal and lateral stacks, as well as the molecular orientation of PI fibre, was improved in the preparation process of fibres. Furthermore, the mechanical properties of fibres are profoundly affected by the heat drawn conditions.

Self-assembly of amphiphilic random co-poly(ionic liquid)s: the effect of anions, molecular weight, and molecular weight distribution

Self-assembly behavior of amphiphilic random co-poly(ionic liquid)s in aqueous solution was investigated in this work. An imidazolium-type homopolymer, poly(1-(4-vinylbenzyl)-3-methyl imidazolium chloride) (denoted as PIL-[Cl]), was synthesized via reversible addition fragmentation chain transfer (RAFT) polymerization of p-chloromethyl styrene, and followed by post-polymerization with methylimidazole (or vinylimidazole). Partial anion-exchange of PIL-[Cl] with PF6− anions yielded amphiphilic random copolymers, PIL-[Cl]x[PF6]y (suffixes x, y represent the relative molar ratio of Cl− and PF6− anions). Self-assembly morphologies of PIL-[Cl]x[PF6]y in aqueous solution as a function of copolymer composition (anions), molecular weight, and molecular weight distribution were investigated. The size of well-defined PIL-[Cl]x[PF6]y spherical micelles increased dramatically with increasing molecular weight distribution, while the anions and molecular weight show little effect on the micelle size. Furthermore, self-assembly of amphiphilic random ionic copolymers with the vinylimidazole groups yielded colloidosomes, which might be due to the polymerization of vinylimidazole groups.

The properties, morphology and structure of BPDA/ PPD/ BOA polyimide fibers

AbstractA family of random copoly(amic acid)s (coPAAs) containing the 2-(4- aminophenyl)-5-aminobenzoxazole (BOA) moiety were synthesized in DMAc, followed by dry-jet wet spinning process into as-spun PAA fibers. The modified polyimide (PI) fibers were obtained from PAA fibers after imidized and drawn in a furnace. The mechanical properties of fibers were improved by incorporating BOA into BPDA/PPD backbone. SEM photo showed that the cross-section of each stage fibers was round and voids free. Besides, the “skin-core” and microfibrillar structure were not observed. The thermal properties of PI fibers were also investigated. The results showed that the PI fibers owned excellent thermal stability, moreover, the dimensional stability and the microphase separation of fibers were improved by heat-drawn stage. The Tg were found to be around 290°C by TMA and DMA. The X-ray (WAXD and SAXS) experiments indicated that the longitudinal stacks, the molecular orientation and the structural homogeneity of PI fiber were improved in the preparation process of fibers.

Thermal and thermo-oxidative degradations of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO)/copoly(aryl ether sulfone) P(ESES-co-EES) block copolymers: a kinetic study

The thermal degradation of a series of three novel ABA block copolymers of different molar mass (M n), were the block A is a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), while the block B is a random copoly(aryl ether sulfone) P(ESES-co-EES), was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres, to investigate the effects of M n of the central block on the thermal stability. Copolymers were synthesized with a two step method: in the first stage, a linking molecule is selectively attached as end group to the P(ESES-co-EES) which reacts in the second step with the phenolic hydroxyl group of PPO. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates, and the characteristic parameters of thermal stability, namely initial decomposition temperature (T i) and the activation energy (E a) of degradation, of the various copolymers were determined. Both T i and degradation E a values increased exponentially as a function of M n of copolymers. The results were discussed and interpreted.

Blockiness and Sequence Polydispersity Effects on the Phase Behavior and Interfacial Properties of Gradient Copolymers

We consider the influence of sequence polydispersity upon the phase behavior and interfacial characteristics of gradient copolymers. By adapting the algorithmic procedure proposed for random copoly...

Styrene-Spaced Copolymers Including Anthraquinone and β-O-4 Lignin Model Units: Synthesis, Characterization and Reactivity Under Alkaline Pulping Conditions

A series of random copoly(styrene)s has been synthesized via radical polymerization of functionalized anthraquinone (AQ) and β-O-4 lignin model monomers. The copolymers were designed to have a different number of styrene spacer groups between the AQ and β-O-4 lignin side chains aiming at investigating the distance effects on AQ/β-O-4 electron transfer mechanisms. A detailed molecular characterization, including techniques such as size exclusion chromatography, MALDI-TOF mass spectrometry, and (1)H, (13)C, (31)P NMR and UV-vis spectroscopies, afforded quantitative information about the composition of the copolymers as well as the average distribution of the AQ and β-O-4 groups in the macromolecular structures. TGA and DSC thermal analysis have indicated that the copolymers were thermally stable under regular pulping conditions, revealing the inertness of the styrene polymer backbone in the investigation of electron transfer mechanisms. Alkaline pulping experiments showed that close contact between the redox active side chains in the copolymers was fundamental for an efficient degradation of the β-O-4 lignin model units, highlighting the importance of electron transfer reactions in the lignin degradation mechanisms catalyzed by AQ. In the absence of glucose, AQ units oxidized phenolic β-O-4 lignin model parts, mainly by electron transfer leading to vanillin as major product. By contrast, in presence of glucose, anthrahydroquinone units (formed by reduction of AQ) reduced the quinone-methide units (issued by dehydration of phenolic β-O-4 lignin model part) mainly by electron transfer leading to guaiacol as major product. Both processes were distance dependent.

Polymer-induced liquid precursor (PILP) phases of calcium carbonate formed in the presence of synthetic acidic polypeptides—relevance to biomineralization

Polymer-induced liquid precursor (PILP) phases of calcium carbonate have attracted significant interest due to possible applications in materials synthesis, and their resemblance to intermediates seen in biogenic mineralisation processes. Further, these PILP phases have been formed in vitro using polyelectrolytes such as poly(aspartic acid) which bears many structural parallels to the highly acidic biomacromolecules that are associated with biogenic calcium carbonate. This article describes experiments which investigate how the composition of acidic polypeptides determines their ability to form PILP phases of CaCO3, and therefore whether it is feasible that the acidic biomacromolecules extracted from CaCO3 biominerals could also function in this way. A series of random copoly(amino acid)s constructed from 80–20%, 50–50% and 20–80% aspartic acid and serine residues were synthesised and their effect on CaCO3 precipitation was determined. A strong correlation between the composition and function of the polypeptide was observed. Only the polypeptide containing 80% aspartic acid residues (Asp80%–Ser20%) induced the formation of continuous CaCO3 films, which provide a fingerprint of an intermediary PILP phase, while addition of Mg2+ also facilitated the formation of expanded film-like structures with the polypeptide Asp50%–Ser50%. In contrast, the weakly-acidic polypeptide Asp20%–Ser80% had only a minor effect on the crystal morphologies and also failed to aid infiltration of CaCO3 into small pores. These results therefore demonstrate that counter-ion induced phase separation of highly acidic biomacromolecules proteins appears to be entirely feasible based upon their composition, but that evidence for the operation of this mineralisation mechanism in vivo is still required.

New Silicone Grafted Copoly(ether imide) from 4,4′-(hexafluoro-isopropylidene)diphthalic Anhydride

A new copoly(ether imide) 1a was synthesized from 4,4′-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA) and 4,4′- bis [3′-trifluoromethyl-p-aminobiphenyl ether)biphenyl (TFBB) with 20 wt% loading of 3,5-diaminobenzoate terminated polydimethylsiloxane (DBPDMS) by solution imidization technique. The copoly(ether imide) showed a glass transition temperature of 272°C by differential scanning calorimetry and of 300°C by dynamic mechanical analysis, respectively. The polymer showed thermal stability up to 371°C for 5% wt loss in synthetic air. Dynamic mechanical analysis showed storage modulus as high as 1.62 GPa at 40°C. In the DMA plot a distinct sub Tg relaxation was observed at 130°C. The copolyimide formed tough transparent film, with tensile strength up to 47 MPa, a modulus of elasticity up to 1.83 GPa and elongation at break up to 65%. Thermal, mechanical and surface properties of the copoly(ether imide) have been evaluated and compared with the already reported analogous random copoly(ether imide) containing siloxane unit in the main chain and with the homopolyimide without siloxane unit.

New Fluorinated Poly(imide siloxane) Random and Block Copolymers with Variation of Siloxane Loading

Several new random and block copoly(imide siloxane)s have been prepared by the solution polycondensation of commercially available 4,4′-oxydianiline (ODA) and amino-propyl terminated polydimethylsiloxane (APPS) with 4,4′-(hexafluoro-isopropylidene)diphthalic anhydride (6FDA). The siloxane loading was kept to 10, 20, 30, 40 and 50 wt% in the copolymers. The random copolymers were prepared by a one pot solution imidization technique, and two pot solution imidization technique was adopted for the synthesis of the block copolymers. The diamine ODA and the dianhydride 6FDA composed the hard block segment, while APPS and 6FDA composed the soft block segment. The hard block length was kept constant while the soft block lengths were varied by varying the siloxane loading. Accordingly, block copoly(imide siloxane)s were prepared on increasing the soft block lengths (DP) from 3 to 6, 10, 18 and 36 for fixed hard block length of 22. The resulting polymers have been well characterized by IR, NMR and GPC techniques. Thermal and mechanical properties of the random and block copolymers were compared with the already reported homopolyimide without siloxane moiety.

Synthesis of amorphous copoly(thioether sulfone)s with high refractive indices and high Abbe numbers

New thermoplastic random copoly(thioether sulfone)s with high refractive indices and high Abbe numbers have been developed by the simultaneous introduction of sulfide, sulfone, and alicyclic units in the polymer chains. They were prepared by random copolymerization of 2,5-bis(sulfanylmethyl)-1,4-dithiane (BMMD) and cyclohexane-1,4-dithiol (CHDT) with divinyl sulfone (DVS) based on the Michael polyaddition. Tough, flexible, colorless and transparent copoly(thioether sulfone) (poly(BMMD/CHDT–DVS)) films were obtained, and they showed good thermal stability with the 5% weight-loss at temperatures over 300 °C in nitrogen, and the glass transition temperatures of 42–50 °C. The inherent amorphous nature of films was confirmed by differential scanning calorimetry. Poly(BMMD/CHDT–DVS) exhibited quite high level of refractive indices and Abbe numbers as thermoplastics, in the range of 1.6512–1.6022 and 42.6–50.6, respectively. The experimental refractive indices and their wavelength dispersions were well reproduced by the DFT calculations with the aid of empirical density prediction.

Local forms of molecular mobility in comb-shaped chromophore-containing copoly(methacrylates)

The local forms of molecular mobility of comb-shaped random copoly(methacrylates) have been studied by the method of dielectric spectroscopy. Side branches of these copolymers are composed of alternating chromophore-containing chains and flexible fluoromethylene sequences. Two regions of relaxation of dipole polarization, γ2 and β processes, related to the mobility of end polar groups and the reorientation of chromophore groups relative to their long axes, respectively, have been discovered in the glassy state. The times of relaxation of the γ2 process depend on the ratio between the flexible and rigid parts of the copolymer. In the region of the β process, the molecular mobility appears to be slightly dependent on the chromophore structure and its intensity is determined by the degree of substitution of chromophore groups.

Synthesis and Thermal Characterization of Some Novel ABA Block Copolymers

AbstractThe synthesis of some novel ABA block copolymers is reported. The block A is a PPO while the block B is a random copoly(aryl ether sulfone), synthesized with three different molecular weights. The block copolymers were obtained by a two step procedure consisting on the functionalization of the random copoly(aryl ether sulfone) followed by a condensation with PPO. Spectroscopic techniques (1H NMR and 13C NMR) were used to characterize the polymers obtained from each step. The NMR data proved the complete conversion of amino groups after the first reaction step and gave some useful insights on the completion of the second step. Copolymer formation is supported by a comparison of the thermal behavior of the block copolymers with respect to the physical blends of the two homopolymers. DSC and DMA analyses showed double glass transitions for the physical blends which could be related to the immiscibility of the two homopolymers, while, in contrast, the block copolymer showed single glass transition. Blends of ABA triblock copolymer/PPO and of ABA triblock/copoly(arylen ether sulfone)s were also prepared. These blends, tested by DSC, showed a good level of compatibility of the ABA copolymer with its singular constituents.magnified image