Segmented Poly Research Articles

Influence of interface interaction on thermal, mechanical and conducting properties of segmented poly (azo-urethane)/carbon nanotube composites

In this research work, solution dispersion technique was employed for the preparation of segmented poly (azo-urethane)/multi-walled carbon nanotube (SPAU/MWCNT) nanocomposites whereas the polyurethane was obtained using single-step procedure. The carboxylated nanotube-based non-compatiblized SPAU/MWCNT and acid chloride functionalized MWCNT-based compatiblized systems were prepared. Afterwards, the hydroxyl end-terminated polyurethane was grafted to acid chloride functional MWCNT through esterification reaction. The grafting to the carboxylated nanotube was achieved via physical interaction. The FTIR spectra confirmed the covalent bonding between the matrix and side-walls of nanotube. Various nanotube loading levels and surface-modified groups were considered to regulate mechanical, thermal and electrical performance of SPAU/MWCNT. The experimental results showed that a moderate loading-level of 5 wt. % MWCNT produced the maximum tensile strength (63.1 MPa) in compatiblized nanocomposites, while the tensile strength of non-compatiblized SPAU/MWCNT was lower (47.25 MPa). Comparative studies based on scanning and transmission electron microscopy of the chemically bonded samples also revealed the covalent coating character and unique nano-fibriller morphology. The dynamic mechanical analysis of nanocomposites showed segmental rigidity due to covalent linking and sample had Tg of 142–152 °C. Addition of acid chloride functionalized MWCNT also contributed to an improvement in the electrical conductivity (2.01-4.31 S cm−1) relative to SPAU/carboxylated MWCNT 1.27-2.86 S cm−1.

Segmented poly(styrene-co-vinylpyridine) as multivalent host for CdSe nanocrystal based nanocomposites

Nanocomposites based on colloidal CdSe nanocrystals (NCs) and a poly(styrene-co-4-vinylpyridine), able to specifically coordinate the NC surface, have been designed and prepared. For first time, the polymer synthesis has been performed by using 2,2,5-tri-methyl-4-phenyl-3-azahexane-3-nitroxide as a mediator, increasing the percentage of 4-vinylpyridine monomeric unit, thus obtaining a random copolymer. The nanocomposite properties have been investigated as a function of NC surface chemistry and copolymer composition, by means of spectroscopic, morphological and structural characterization techniques. An improved uniformity of NC dispersion in the nanocomposite has been found at increased percentage of 4-vinylpyridine in the copolymer. The improved NC dispersion in the nanocomposite films has been discussed in terms of the ability of the copolymer to act as a multivalent ligand. The reported results offer a valuable contribution toward the design and the fabrication of innovative nanocomposite material, formed of copolymers and colloidal NCs, specifically suited for energy conversion applications.

Novel dendritic-poly(urethane-urea) hybrid thin films from hydrogen bond rich dendrons

Hydrogen bond rich segmented poly(urethane-urea) was synthesized from methylene diphenylisocyanate (MDI) and three generations of polyurea-malonamide dendrons as hard segment and polycaprolactone diol as soft segment for thin film applications. The prepared polymers were characterized using spectroscopic, microscopic and thermal analyses. The formation of urethane linkage during the prepolymer reaction and the urea linkage between prepolymer and the dendrons is confirmed by Fourier transform infrared (FTIR) spectroscopy and 1H nuclear magnetic resonance (NMR) spectroscopy. FTIR shows the presence of hydrogen bonding of –NH groups with both urethane carbonyl group from hard segment and the ether group from the soft segment. However, the phase mixing of hard and soft segments decreases with the higher generation dendrons, as evidenced from FTIR. This observation was confirmed by phase images of the atomic force microscopy (AFM). The coating when applied to clean steel substrates via dip coating reveals uniform, dense and essentially defect free morphology. The work demonstrates that the mechanical properties of the hybrid thin films are dependent on the generation of the dendrons and provides a platform for surface engineering with tunable elastic modulus.

Synthesis and characterization of segmented poly(ether ester amide)s from diglycol, adipic acid, and a nylon‐6 oligomer

This article presents a convenient method for synthesizing segmented poly(ether ester amide)s (PEEAs) by polycondensation and chain extension. A nylon‐6 oligomer prepared from ε‐caprolactam and ethanolamine through ring‐opening polymerization was polymerized with adipic acid and diglycol to prepare PEEA prepolymers (PrePEEAs) with ether linkages and amide contents ranging from 20 to 60 mol%. Chain extension of the PrePEEAs was conducted at 200°C using 2,2′‐(1,4‐phenylene)‐bis(2‐oxazoline) and carbonyl biscaprolactamate as combination chain extenders. The chain‐extended PEEAs (ExtPEEAs) were characterized by viscometry, gel permeation chromatography, FT‐IR, 1H‐NMR, differential scanning calorimetry, thermogravimetric analysis, wide angle X‐ray diffraction, and tensile testing. Results show that incorporation of nylon‐6 segments yields semicrystalline ExtPEEAs and that introduction of ether linkages improves the flexibility of the resultant polymers. ExtPEEAs showed Tm from 107.6 to 137.3°C, good thermal stability with initial decomposition temperatures above 337.3°C, and tensile strengths of up to 27.4 MPa with strains at break ranging from 231.24 to 1052.52%. POLYM. ENG. SCI., 55:763–770, 2015. © 2014 Society of Plastics Engineers

Synthesis and characterization of segmented poly(butylene succinate) urethane ionenes containing secondary amine cation

The segmented poly(butylene succinate) urethane ionenes (PBSUI) containing secondary amine cation were synthesized by chain extension reaction of dihydroxyl terminated poly(butylene succinate) and diethanolamine hydrochloride (DEAH) in the presence of hexamethylene diisocyanate. NMR, DSC, WAXD, POM, SAXS, DMA, and rotational rheometer were used to characterize the structure and properties of the PBSUI, and the tensile properties and hydrolytic degradation of the PBSUI were also investigated. All the results suggest that the content of urethane ionic group plays an important role in tuning the properties of the PBSUIs. The crystallization rate increased first and then decreased and the equilibrium melting temperature increased gradually with increasing urethane ionic group content. The maximum crystallization rate was obtained for PBSUI with 3 wt% DEAH. The obvious clusters formed by aggregation of urethane ionic group were evidenced by DMA and SAXS for the PBSUI containing 5 wt% DEAH. The complex viscosity increased significantly with increasing urethane ionic group content due to the physical crosslinking effect resulted from aggregation of ionic groups. The storage modulus increased with DEAH content increased up to 3 wt %, while decreased with further increasing DEAH content. Tensile testing indicated incorporation of urethane ionic group did not change the tensile properties apparently. The hydrolytic degradation rate of the samples increased with the increase in urethane ionic group content which was mainly ascribed to the increased hydrophilicity.

Soft segment composition and its influence on phase-separated morphology of PCL/PEG-based poly(urethane urea)s

A composition-dependent microphase separation of segmented poly(urethane urea)s (PUUs), based on a mixture of two hydrophobic (polycaprolactone) and hydrophilic (polyethylene glycol) polyols, is investigated. Synthesis of PUUs was carried out through the reaction of in situ generated AB-type macromonomers, prepared from the reaction of NCO-terminated urethane prepolymers, with benzoic acid in dimethyl sulfoxide as solvent/reagent at 40–80 °C. The segmented PUUs were characterized by different methods including FTIR and NMR spectroscopies, gel permeation chromatography, differential scanning calorimetry and dynamic mechanical analysis. Microphase separation in the synthesized PUUs was monitored using atomic force microscopy (AFM) to find a better insight into structure–property relationship of PUUs consisting of mixed polyols. Thermal analysis of the polymers revealed that by introducing poly(ethylene glycol) (PEG) in PUU backbone, a well-defined glass transition was obtained. The results of AFM showed that PCL-based poly(urethane urea) has a morphology in which hard segment domains were homogeneously distributed in the soft segment matrix. In the samples based on PCL/PEG, the hard segment domains aggregates were connected to each other and were inhomogeneously distributed in the matrix. Comparison of the overall data revealed that the differences in soft segment compositions had a marked effect on the molecular structure and the mechanical properties of PUUs.

Helical Self-Assemblies of Segmented Poly(phenylenevinylene)s and Their Hierarchical Donor–Acceptor Complexes

We report aromatic π-stack-driven helical self-assemblies of segmented poly(phenylenevinylene)s and their hierarchical helical donor–acceptor assemblies with electron deficient molecules by a solvent-induced self-organization process. New segmented PPVs were designed and synthesized having tricyclodecane-substituted oligophenylenevinylene (OPV) π-core with flexible methylene chains of variable carbon atoms 4, 8, and 12. The polymers were obtained in high molecular weights with very good solubility in common organic solvents. The polymers were found to be amorphous, and their glass transition temperature varied from 100 to 170 °C with respect to the increase in the rigidity of the polymer backbone. The flexible segmented polymer underwent aromatic π-stack interaction to produce π-conjugated polymer aggregates in methanol and tetrahydrofuran (THF) solvent combinations. Electron microscopic studies confirmed that these π-aggregates appeared as bundles of helical assemblies. An electron deficient perylenebisimide derivative was complexed with segmented polymers to produce stable and helical donor–acceptor hierarchical assemblies. The formation of D–A assemblies was confirmed by detail photophysical studies such as absorbance, emission, time-resolved fluorescence decay, and FRET mechanism. A controlled experiment with structurally identical rigid polymer revealed that appropriate polymer design in the segmented skeleton is essential for making stable helical D–A assemblies. Thus, the present study provides insight into the formation of stable helical donor–acceptor assemblies in π-conjugated polymers that are useful for application in optoelectronics.

Biodegradable poly(ester urethane) urea scaffolds for tissue engineering: Interaction with osteoblast-like MG-63 cells

Porous three-dimensional scaffolds with potential for application as cancellous bone graft substitutes were prepared from aliphatic segmented poly(ester urethane) urea using the phase-inverse technique. Proton nuclear magnetic resonance, size-exclusion chromatography, electron spectroscopy for chemical analysis, secondary ion mass spectrometry, infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, computed tomography and mechanical tests were carried out, to characterize the scaffolds’ physicochemical properties. Human osteosarcoma MG-63 cells were seeded into the scaffolds for 1, 2, 3 and 4weeks to evaluate their potential to support attachment, growth and proliferation of osteogenic cells. The scaffold–cell interaction was assessed by analysis of DNA content, total protein amount, alkaline phosphatase activity and WST-1 assay. The scaffolds supported cell attachment, growth and proliferation over the whole culture period of 4weeks (DNA, total protein amount). There was, however, a reduction in the WST-1 assay values at 4weeks, which might suggest a reduction in the rate of cell proliferation at this time.

Synthesis and characterization of aliphatic segmented poly(ether amide urethane)s through a non-isocyanate route

Two nylon-6 oligomers with polymerization degrees (DP or n) of 6.82 and 4.52 terminated with H2N- and HO-groups (H2N–PAn–OHs) were prepared from caprolactam with ethanolamine via ring-opening polymerization at different molar ratios, and transformed into HO-terminated nylon-6 oligomers (HO–PAn–OHs) through reaction with excess caprolactone. Melt polycondensation of the HO–PAn–OHs, with 1,6-bis(hydroxyethyloxy carbonyl amino)hexane (BHCH) and polyethylene glycols (PEGs), was performed at 170 °C under normal pressure and at 180 °C under reduced pressure of 3 mmHg at different periods. A series of novel aliphatic thermoplastic poly(ether amide urethane)s with different short nylon-6 and PEG segments (s-PEAUs) was prepared. The obtained s-PEAUs were characterized by gel permeation chromatography, FTIR, 1H-NMR, 2D 1H–1H COSY NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray scattering, and tensile tests. The s-PEAUs exhibited an Mn up to 18 400, an Mw up to 48 900, Tm between 145.94 °C and 177.86 °C, initial decomposition temperature of over 253.39 °C, and tensile strength up to 30.03 MPa with elongation at break of 286.8%. Some urea linkages were formed during transurethane polycondensation.

Surface characterization, hemo- and cytocompatibility of segmented poly(dimethylsiloxane)-based polyurethanes

Segmented polyurethanes based on poly(dimethylsiloxane), currently used for biomedical applications, have sub-optimal biocompatibility which reduces their efficacy. Improving the endothelial cell attachment and blood-contacting properties of PDMS-based copolymers would substantially improve their clinical applications. We have studied the surface properties and in vitro biocompatibility of two series of segmented poly(urethane-dimethylsiloxane)s (SPU-PDMS) based on hydroxypropyl- and hydroxyethoxypropyl- terminated PDMS with potential applications in blood-contacting medical devices. SPU-PDMS copolymers were characterized by contact angle measurements, surface free energy determination (calculated using the van Oss-Chaudhury-Good and Owens-Wendt methods), and atomic force microscopy. The biocompatibility of copolymers was evaluated using an endothelial EA.hy926 cell line by direct contact assay, before and after pre-treatment of copolymers with multicomponent protein mixture, as well as by a competitive blood-protein adsorption assay. The obtained results suggested good blood compatibility of synthesized copolymers. All copolymers exhibited good resistance to fibrinogen adsorption and all favored albumin adsorption. Copolymers based on hydroxyethoxypropyl-PDMS had lower hydrophobicity, higher surface free energy, and better microphase separation in comparison with hydroxypropyl-PDMS-based copolymers, which promoted better endothelial cell attachment and growth on the surface of these polymers as compared to hydroxypropyl-PDMS-based copolymers. The results showed that SPU-PDMS copolymers display good surface properties, depending on the type of soft PDMS segments, which can be tailored for biomedical application requirements such as biomedical devices for short- and long-term uses.

Biodegradable Poly(ester-urethane)s Containing Poly(butylene succinate) and Mesogen Segments

A series of biodegradable segmented poly (ester-urethane) s were prepared by solution polymerization of poly (butylene succinate) (PBS), mesogenic diol (MD), and hexamethylene diisocyanate (HDI). The MD content was varied from 0 to 40 mol% so that the effects of the mesogen content on the thermal and physical properties, and enzymatic degradation were examined respectively. It was found that introducing mesogen segments could increase the thermal stability and the elastic properties, while reduced the phase transition temperatures, the degree of relative crystallinity (Xc) and the enzymatic degradation rate.

Inelastic response of copolyurethane elastomers with varying soft segment molecular weights and preparation procedure

A family of thermoplastic polyurethane elastomers (TPUs) based on the soft segment poly(oxytetramethylene) (PTMO2000 and PTMO1000) were synthesized by the one-shot and prepolymer methods. Two hard segments were chosen, 4,4′-methylenebis(phenyl isocyanate) (MDI) (non-crystallizable) and 4,4′-dibenzyl diisocyanate (DBDI) (crystallizable). Microphase separation and crystallinity were investigated using small-angle X-ray scattering and wide-angle X-ray scattering, and dynamic viscoelastic properties were also determined. An increased hard phase degree of crystallinity was primarily achieved by use of DBDI instead of MDI, regardless of the preparation procedure and soft segment molecular weight. An increase of the molecular weight leads to an increase in phase separation and to a decrease in hysteresis. For the DBDI based polymers, a lower soft segment molecular weight resulted in an increase in crystallinity. The DBDI series of TPUs obtained by the one-shot and prepolymer methods showed higher hysteresis and residual elongations compared with the corresponding materials achieved with MDI. Although the materials varied widely in response to first loading, regardless of the preparation procedure, they displayed remarkable reproducibility and commonality in cyclic responses within the maximum strain envelope. The thermomechanical experiments revealed a better thermal behavior with increase of the soft segment molecular weight from PTMO1000 to PTMO2000.© 2013 Society of Chemical Industry

Siloxane‐based segmented poly(urethane‐urea) elastomer: Synthesis and characterization

ABSTRACTA series of segmented poly(urethane‐urea) block copolymers were synthesized with varying proportions of polydimethylsiloxane diols in combination with polytetramethylene ether glycol (PTMG) using 4,4'‐methylenediphenyl diisocyanate followed by chain extension with a (50:50 mol %) mixture of 4,4'‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (M‐CDEA) and 1,4‐butanediol (BD). The molecular structures of polydimethylsiloxane urethane‐ureas were characterized by ATR‐FTIR and 1H‐NMR spectroscopic techniques. Distribution of siloxane domain and its influence on surface roughness were investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM), respectively. The mechanical and thermal properties of the elastomers were studied by thermogravimetric analysis, dynamical mechanical thermal analysis, and tensile measurement. The results showed that by incorporation of polydimethylsiloxane diol and M‐CDEA chain extender in polyurethane formulation, some improvements in thermal stability, fire resistance and surface hydrophilicity were achieved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1743–1751, 2013

High yield and stereospecific synthesis of segmented poly (p-phenylene vinylene) by the Heck reaction

A new block copolymer comprised of a 2,5 (p-phenylene vinylene) unit alternating with a hexamethylene unit was synthetized by the Heck methodology using phosphite ligands and two different sources of palladium, with high yields and good polymerization degrees. The spectral characteristics of the polymer are in good agreement with those of its oligomer analogue and its quantum yield (as high as 0.78 vs quinine sulfate as standard) showed to be dependant on the source of palladium employed for the Heck reaction.

Characterization and biocompatibility studies of new degradable poly(urea)urethanes prepared with arginine, glycine or aspartic acid as chain extenders

Polyurethanes are very often used in the cardiovascular field due to their tunable physicochemical properties and acceptable hemocompatibility although they suffer from poor endothelialization. With this in mind, we proposed the synthesis of a family of degradable segmented poly(urea)urethanes (SPUUs) using amino acids (L-arginine, glycine and L-aspartic acid) as chain extenders. These polymers degraded slowly in PBS (pH 7.4) after 24weeks via a gradual decrease in molecular weight. In contrast, accelerated degradation showed higher mass loss under acidic, alkaline and oxidative media. MTT tests on polyurethanes with L-arginine as chain extenders showed no adverse effect on the metabolism of human umbilical vein endothelial cells (HUVECs) indicating the leachables did not provoke any toxic responses. In addition, SPUUs containing L-arginine promoted higher levels of HUVECs adhesion, spreading and viability after 7days compared to the commonly used Tecoflex(®) polyurethane. The biodegradability and HUVEC proliferation on L-arginine-based SPUUs suggests that they can be used in the design of vascular grafts for tissue engineering.

Synthesis and properties of poly(imide siloxane) block copolymers with different block lengths

AbstractSeveral poly(imide siloxane) block copolymers with the same bis(γ‐aminopropyl)polydimethylsiloxane (APPS) content were prepared. The polyimide hard block was composed of 4,4′‐oxydianiline and 3,3′,4,4′‐diphenylthioether dianhydride (TDPA), and the polysiloxane soft block was composed of APPS and TDPA. The length of polysiloxane soft block increased simultaneously with increasing the length of polyimide hard block. For better understanding the structure–property relations, the corresponding randomly segmented poly(imide siloxane) copolymer was also prepared. These copolymers were characterized by FT‐IR, 1H‐NMR, dynamic mechanical thermal analysis, thermogravimetric analysis, polarized optical microscope, rheology and tensile test. Two glass transition temperatures (Tg) were found in the randomly segmented copolymer, while three Tgs were found in the block copolymers. In addition, the Tgs, storage modulus, tensile modulus, solubility, elastic recovery, surface morphology and complex viscosity of the copolymers varied regularly with increasing the lengths of both blocks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Characterization of Shape-Memory Trifunctionally Cross-Linked Polyurethanes, with Varying Hard and Soft Segments

A family of potential shape-memory trifunctionally cross-linked polyurethanes (SMPs) was achieved with varying the hard segments. The molecular weight of the soft segment poly(oxytetramethylene) (PTMO) was held constant. The polymers were employed with and without chain extender. They were characterized by means of structural studies and creep tests over a range of temperatures, and hence their shape-memory performance was determined. More crystallization was observed in the materials with hard domains based on the flexible diisocyanate 4,4′-dibenzyl diisocyanate (DBDI) extended with 1,4-butanediol (BDO). A series of key parameters characterizing shape-memory performance was determined: the temperature position of the peak (Tpeak), the half-width of the peak (δT), and the minimum value of the 30 s isochronal creep modulus E(30 s) Emin. While the peak temperature and modulus increased with increasing cross-link density, the width of the peak was observed to decrease with increasing cross-link density. The materials were found to vary systematically with details of the network structure.

Synthesis and Properties of Biodegradable Liquid Crystalline Poly(ester-Urethane)s Based on Poly(L-Lactic Acid)

A series of biodegradable segmented liquid crystalline poly(ester-urethane)s were prepared by solution polymerization of poly(L-lactic acid) (PLLA), mesogenic diol prepolymer poly(butylene terephthaloyldioxy dibenzoates) (MD), and hexamethylene diisocyanate (HDI). The MD content was varied from 0 to 40 mol% so that the effects of the mesogen content on the thermal and physical properties, and hydrolytic degradation were examined respectively. It was found that introducing mesogens units could increase the thermal stability and the elastic properties, while reduced the phase transition temperatures and the hydrolytic degradation rate.

Synthesis of Poly (methyl methacrylate)/Zinc Oxide Nanocomposite with Core-Shell Morphology by Atom Transfer Radical Polymerization

A method to prepare zinc oxide (ZnO) nanoparticles with a covalently bonded poly(methyl methacrylate) (PMMA) shell by surface initiated atom transfer radical polymerization (ATRP) was reported. First, the initiator for ATRP was covalently bonded onto the surface of zinc oxide nanoparticles through our novel method. Firstly, the surface of ZnO nanoparticle was treated with 3-aminopropyl triethoxysilane, a silane coupling agent, and then this functionalization nanoparticle was reacted with α-chloro phenyl acetyl chloride to prepare atom transfer radical polymerization macroinitiator. The metal-catalyzed radical polymerization of MMA with ZnOmacroinitiator was performed using a copper catalyst system to give the ZnO-based nanoparticles hybrids linking PMMA segments (poly (methyl methacrylate)/zinc oxide nanocomposite). These hybrid nanoparticles had an exceptionally good dispersability in organic solvents and were subjected to detailed characterization using FTIR, TEM and TGA and DSC analyzed.

Physical and thermal properties of thermoplastic poly(azo-urethane)s

New thermoplastic segmented poly(azo-urethane)s (PAUs) have been synthesized by one-step polycondensation from aromatic diazo-diol, ( E)-1-(4-(4-(3-hydroxypyridyl-azo)thiocarbamoylaminobenzyl)-phenyl)-3-(3-hydroxypyridylazo)thiourea, as chain extenders, phenylene diisocyanate and 20–60 mol % polyethylene glycol (PEG) with the molecular weight of 2000 g/mol. The effect of diazo-diol used in the structure and some physicochemical, thermal and mechanical properties of the segmented polyurethanes were studied. The structure was examined by proton nuclear magnetic resonance (1H NMR) and Fourier-transform infrared spectroscopy (FTIR) analyses. Polyazos were the products with good processability and high molar mass in the range 120 × 103–135 × 103 g/mol. Thermal properties, investigated by thermogravimetric analysis and differential scanning calorimetry indicated that PAUs up to 40 mol % polyol were fairly stable above 530°C, having initial weight loss of around 528–539°C, 10% gravimetric loss in the range 553–567°C and own high glass transition temperature 259–264°C. The polymers also demonstrated higher tensile strength (56.53–63.83 MPa) and elongation at break (1.58–1.63). However, compared with typical polyurethanes, PAUs with lower polyol content displayed higher Tgs, heat and mechanical stability owing to warily designed rigid hard segment structure.