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The Dissipative Particle Dynamics (DPD) simulation technique was used to elucidate the composition-dependent equilibrium morphological behavior of three different symmetric ABA triblock copolymers, which were; poly(e-caprolactone)-poly(dimethylsiloxane)-poly(e-caprolactone) (PCL-PDMS-PCL), poly(e-caprolactone)-poly(ethylene oxide)-poly(e-caprolactone) (PCL-PEO-PCL) and poly(L-lactide)-poly(dimethylsiloxane)-poly(L-lactide) (PLLA-PDMS-PLLA). These polymers were chosen due to their biomedical and biotechnological importance. Polymeric A and B blocks were modeled as connected chain of beads with varying incompatibility. The impact of the block incompatibilities on the microphase separation as well as on the equilibrium phase behaviors were investigated at the mesoscopic scale. A detailed visual analysis of the DPD images and constructed phase diagram showed that quite different equilibrium morphologies were attainable by controlling the molecular weights of the blocks and the strength of the intermolecular interaction between them. More compatible A and B blocks underwent lamellar to cylindrical and cylindrical to spherical phase transitions at lower B block concentrations. Our results clearly showed that, Flory–Huggins interaction parameter (χ) and degree of polymerization (N) were the only control parameters, which determined the shape and size of the phase domains, as well as the extent of equilibrium nanophase separation. Our DPD simulated morphologies were compared with experimental images obtained by Atomic Force Microscopy (AFM).

There has been a considerable interest in developing stiff, strong, tough, and highly stretchable hydrogels in various fields of science and technology including biomedical and sensing applications. However, simultaneous optimization of stiffness, strength, toughness, and extensibility is a challenge for any material, and hydrogels are well-known to be mechanically weak materials. Here, we demonstrate that poly(ethylene oxide)-based dual stimuli-responsive semicrystalline poly(urethane-urea) (PU) copolymers with high hard segment contents (30 and 40%) can be utilized as stiff, strong, tough, and highly stretchable hydrogels with an elastic modulus (4-10 MPa) tens to hundreds of times higher than that of conventional hydrogels (0.01-0.1 MPa), strength (7-13 MPa) and toughness (53-74 m(-3) MJ. m(-3)) fairly comparable to those of the toughest hydrogels reported in the literature, and stretchability beyond 10 times their initial length (1000-1250%). In addition, the shape-memory program has been used to tune the room temperature stiffness and strength of the studied PU copolymers. Finally, the materials show fast shape recovery (less than 10 s) during both heat- and water-activated shape memory cycles, which can be adjusted by a simple modulation of the hard segment content and/or soft segment molecular weight. Our findings may be of interest in emerging biomedical and sensing applications.

Achieving a unique combination of stiffness, strength, extensibility, and toughness in sol-cast poly(urethane-urea) (PU) copolymer films is a challenge since these properties are-in general- mutually exclusive. Here we demonstrate that geometric confinement of the basic building blocks controls stiffness, strength, extensibility, and toughness in PU films. Our results suggest that the severity of geometric confinement can be tuned by adjusting (i) soft segment molecular weight (SSMW) and (ii) drying temperature (DT) thanks to their effects on the structure formation via microphase separation and/or (confined and/or bulk) crystallization. It is therefore possible to produce (i) soft (no notable confinement) and (ii) stiff, strong, extensible, and tough (severe confinement) materials without changing any other parameter except SSMW and DT. The former has a typical physically cross-linked network and shows a welldefined elastomeric behavior with an elastic modulus (E) of 5-20 MPa, a tensile strength (sigma(max)) of 30-35 MPa, an extensibility (epsilon) of 1000-1300%, and a toughness (W) of 90-180 MJ m(-3). The latter, on the other hand, possesses an elegant hierarchical structure containing tightly packed secondary structures (7(2)-helix, 4(1)-helix, and antiparallel beta-sheets) and displays an elastoplastic behavior with an E of 400-700 MPa, a sigma(max) of 45-55 MPa, an epsilon of 650-850%, and a W of 200-250 MJ m(-3). Hence, our findings may be of interest in designing advanced materials containing synthetic replica of the secondary structures found in protein-based materials. The structure formation in the materials with this structural hierarchy is driven by the confined crystallization of helical poly(ethylene oxide) (PEO) chains in subnanometer urea channels, which-to the best of our knowledge-is a phenomenon wellknown in host-guest systems but has not yet demonstrated in PU copolymers, and complemented by the "bulk" crystallization of PEO and/or the microphase separation.

Poly(e-caprolactone)–polydimethylsiloxane–poly(e-caprolactone) (PCL-PDMS-PCL) triblock copolymers with a wide range of block lengths (1000–32,000 g/mol) were synthesized by the ring-opening polymerization of e-caprolactone using aminopropyl terminated PDMS oligomers as the initiator. Reactions were carried out in bulk or solution at 125 ± 5 °C under the catalytic action of tin octoate. Products obtained in high yields were characterized by FTIR spectroscopy, gel permeation chromatography, X-ray diffraction, temperature-dependent optical microscopy, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and static water contact angle measurements. Effect of the polymer composition and the molecular weight of the PDMS and PCL blocks on; (i) copolymer morphology and the extent of microphase separation, (ii) crystallization of PCL segments and (iii) surface properties of copolymers were investigated. Regardless of the block lengths, all PCL-PDMS-PCL copolymers displayed well microphase separated morphologies. The extent of microphase separation, resultant morphology and sizes of the microphases were strongly dependent on the copolymer composition and the block lengths of both PCL and PDMS segments. Crystalline PCL microphase was observed in all copolymers, which increased as a function of PCL content and molecular weight. Hydrophobicity of the copolymer surfaces was improved with increasing PDMS molecular weight, as determined by static water contact angle measurements.

Quantum mechanical calculations (QMC) and dissipative particle dynamics (DPD) simulations were utilized to understand the nature of the short and long-range hydrogen bonding and its influence on the microphase morphology in segmented polyurethanes and segmented polyureas prepared without chain extenders through the stoichiometric reactions of hydroxy or amine terminated poly(tetramethylene oxide) (PTMO-1000) with 1,4-phenylene diisocyanate (PPDI) and 1,3-phenylene diisocyanate (MPDI). The possibility of long-range connectivity due to a network of well-ordered hydrogen bonds between symmetrical PPDI and kinked MPDI based model urethane and urea compounds were also investigated. Special emphasis was given on the understanding of the influence of diisocyanate symmetry and nature of the hydrogen bonding between hard segments on the morphology development. QMC results obtained clearly indicated the possibility of long-range ordering of hydrogen bonds between PPDI based urethane and urea groups, while MPDI based systems did not display such a behavior. DPD results strongly supported the QMC studies and clearly demonstrated the possibility of long-range connectivity of hydrogen bonds between urethane and urea groups in PPDI based segmented copolymers, leading to the formation of microphase separated morphologies in these systems, which was not observed in the kinked MPDI based segmented urethane and urea copolymers. Computational results obtained strongly supported the experimental observations reported on the morphology and thermal and mechanical properties of these segmented polyurethanes and polyureas based on PPDI and MPDI.

A comprehensive survey of the recent developments on the synthesis, properties and applications of silicone containing copolymers is provided. Influence of (-R2Si-O-) backbone composition on the physicochemical properties of silicone copolymers, such as thermal transitions, solubility parameter and surface tension is discussed. Preparation and properties of well-defined am-reactive organofunctionally terminated (telechelic) silicone oligomers and their utilization in the preparation of a wide range of block and segmented copolymers through step-growth, anionic, ring-opening and living free-radical polymerization techniques are provided. Use of silicone oligomers in the modification of polymeric network structures is also discussed. Special emphasis is given to the discussion of the effect of silicone oligomer and organic segment structure and molecular weight on the morphology and surface and bulk properties of the resultant silicone containing copolymers and networks., NA

Hydrophilization of polydimethylsiloxane–urea copolymer (PSU) surfaces and the extent of hydrophobic recovery were investigated as a function of; (i) UV/ozone (UV/O) exposure time, (ii) the aging period after UV/O exposure, (iii) sample preparation method, and (iv) polydimethylsiloxane (PDMS) soft segment molecular weight of the copolymer (1500, 3000 and 11,000 g/mol). All copolymers had a constant urea hard segment content of 15% by weight. Samples were prepared by three different methods, which were; solution casting, spin-coating and electrospinning. XPS spectra clearly showed transformation of PDMS into SiO 2 and sub-oxides, which increased gradually with increasing UV/O exposure time. XPS and ATR-FTIR measurements also revealed that the copolymer based on PDMS-11000 displayed the highest amount of SiO 2 formation and overall surface modification. Static water contact angle values of the spincoated silicone–urea copolymer films decreased significantly from 110° to 43° after 3 h of UV/O exposure. Interestingly, the hydrophobicity of the electrospun fibers was retained under similar UV/O exposure conditions, most probably due to the preserved surface roughness. Hydrophobic recovery was evaluated after 2 months of storage at ambient conditions. The slowest recovery was observed for spin-coated copolymer film based on PDMS-11000, due to higher amount of surface oxidation and formation of a thicker SiO 2 barrier layer.

The effect of poly(ethylene oxide) (PEO) soft segment molecular weight (M-n = 2000, 4600 and 8000 g mol(-1)) on the glass transition, crystallinity, molecular mobility and segmental dynamics of a series of aliphatic polyurethaneurea copolymers (PUU) with a constant hard segment content of 30% by weight was investigated using differential scanning calorimetry and dielectric relaxation spectroscopy. The soft segment (PEO) glass transition temperature increased with increasing molecular weight. Furthermore, five different relaxations were observed in dielectric analyses of all copolymers. These included local glassy state motions (gamma) and (beta), segmental motion of the soft phase (alpha), conductivity relaxation, and interfacial Maxwell-Wagner-Sillars (MWS) polarization. Local relaxations follow Arrhenius behavior and their time scale is not affected by the soft segment molecular weight. alpha-Relaxation follows Vogel-Tammann-Fulcher (VTF) behavior and is slower for the copolymer based on PEO-4600. Conductivity relaxation and the interfacial MWS polarization also follow VTF behavior and have quite similar slopes since both are related to the same phenomena. Unexpectedly, the interfacial MWS polarization is not affected by the soft segment molecular weight. Although this result suggests that the soft segment molecular weight does not affect the microphase separation in these copolymers, we believe that no safe conclusions can be extracted for this system due to the high complexity and the presence of many phases with different conductivity. However, significant differences were observed in the conductivity relaxation, which is much faster for the copolymer based on PEO-2000, due to its lower crystallinity when compared with others.

Highly hydrophobic surfaces of silicone–urea copolymers were transformed into hydrophilic ones upon UV/ozone treatment. The extent of surface modification was strongly dependent on the sample preparation method and the exposure time. The physical and chemical changes at the copolymer surfaces were analyzed by spectroscopic (XPS, ATR-FTIR), microscopic (SEM) techniques and static water contact angle measurements. ATR-FTIR spectra clearly showed the dramatic change in the strongly hydrogen bonded urea hard segments and the degradation of dimethylsiloxane units in silicone–urea copolymers. XPS results revealed the formation of SiO x on the surface, which gradually increased with exposure time. After 3 h of UV/ozone exposure, Si(2p) binding energy shifted from 101.9 to 102.85 eV, which is a clear indication of an increase in the oxidation state of silicon. The deterioration of microroughness of the electrospun webs upon UV/ozone exposure, which was revealed by SEM, resulted in a dramatic decrease in the static water contact angle values from 129 to 62°. These results clearly show that UV/ozone process is a very simple and facile method to transform hydrophobic silicone–urea copolymer surfaces into fairly hydrophilic ones.

Effect of polydimethylsiloxane (PDMS) soft segment molecular weight (Mn = 3200, 10,800 and 31,500 g/mol) and urea hard segment content (2.0–11.4% by weight) on the hysteresis and permanent set behavior of segmented silicone-urea (TPSU) copolymers were investigated. In spite of very low hard segment contents, all copolymers formed self-supporting films and displayed good mechanical properties. When the mechanical hysteresis and set behavior of the silicone-urea copolymers with similar hard segment contents (around 7.5% by weight) but based on PDMS-3K, PDMS-11K and PDMS-32K were compared, it was very clear that as the PDMS molecular weight increased, hysteresis and instantaneous set values decreased significantly. Copolymers based on the same silicone soft segment (PDMS-11K or PDMS-32K) but with different hard segment contents showed a linear increase in hysteresis and a slight decrease in the instantaneous set as a function of hard segment content. Constant initial stress creep experiments also showed lower creep as the PDMS segment molecular weight increased for copolymers with similar urea contents. Since the critical entanglement molecular weight (Me) of PDMS is stated to be 24,500 g/mol, our results tend to suggest important contribution of chain entanglements on the hysteresis and instantaneous set of these silicone-urea copolymers.

Novel, segmented thermoplastic silicone–urea (TPSU) copolymers based on rather high molecular weight aminopropyl terminated polydimethylsiloxane (PDMS) soft segments ( 10,800 and 31,500 g/mol), a cycloaliphatic diisocyanate (HMDI) and various diamine chain extenders were synthesized. Copolymers with very low urea hard segment contents of 1.43–14.4% by weight were prepared. In spite of very low hard segment contents, solution cast films showed very good microphase separation and displayed reasonable mechanical properties. Tensile strengths of TPSU copolymers showed a linear dependence on their urea hard segment contents, regardless of the structure of the diamine chain extender used. The modulus of silicone–urea copolymers is dependent on the urea concentration, but not on the extender type or PDMS molecular weight. When silicone–urea copolymers with identical urea hard segment contents were compared, copolymers based on PDMS-31,500 showed higher elongation at break values and ultimate tensile strengths than those based on PDMS-10,800. Since the critical entanglement molecular weight (Me) of PDMS is about 24,500 g/mol, these results suggest there is a significant contribution from soft segment chain entanglement effects in the PDMS-31,500 system regarding the tensile properties and failure mechanisms of the silicone–urea copolymers.

Montmorillonite modified with distearyldimethyl ammonium chloride (C18-QAC) (Nanofil-15) (NF15) was incorporated into polydimethylsiloxane-urea (silicone-urea, PSU) copolymers. PSU was obtained by the reaction of equimolar amounts of aminopropyl terminated polydimethylsiloxane (PDMS) oligomer ( = 3,200 g/mol) and bis(4-isocyanatohexyl)methane (HMDI). A series of PSU/NF15 nanocomposites were prepared by solution blending with organoclay loadings ranging from 0.80 to 9.60% by weight, corresponding to 0.30 to 3.60% C18-QAC. Colloidal dispersions of organophilic clay (NF15) in isopropanol were mixed with the PSU solution in isopropanol and were subjected to ultrasonic treatment. Composite films were obtained by solution casting. FTIR spectroscopy confirmed that the organoclay mainly interacted with the urea groups but not with PDMS. XRD analysis showed that nanocomposites containing up to 6.40% by weight of organoclay had fully exfoliated silicate layers in the polymer matrix, whereas 9.60% loading had an intercalated structure. Physicochemical properties of nanocomposites were determined. PSU/NF15 nanocomposites displayed excellent long-term antibacterial properties against E. coli.

Time-dependent morphology development in segmented polyureas obtained by the stoichiometric reactions between amine terminated poly(tetramethylene oxide) (PTMO) and aromatic diisocyanates were investigated. Polyureas were prepared by reacting aminopropyl terminated PTMO oligomer (Mn = 1100 g/mol) and various aromatic diisocyanates, such as 1,4-phenylene diisocyanate (PPDI), 1,3-phenylene diisocyanate (MPDI), diphenylmethane diisocyanate (MDI), and tolylene diisocyanate (TDI). Time-dependent FTIR studies were conducted on thin films cast onto KBr discs, which were annealed at 200 °C for 10 min in an air oven. After removing from the oven, samples were placed into the FTIR spectrometer at room temperature, where time-dependent spectra were recorded until equilibrium was reached. Time-dependent peak reorganization in 3500–3100 cm−1 (NH region), 1750–1450 cm−1 (CO region or amide I and amide II regions), and 1180–1020 cm−1 (COC) were monitored. Depending on the chemical structure and the symmetry of the diisocyanate, major differences were observed in the time needed to reach an equilibrium morphology in these homologous poly(ether urea) copolymers. Symmetric PPDI-based polyurea reached equilibrium in about 1 h compared with its asymmetric MPDI-based counterpart, which needed about 150 h. Microphase development of the MPDI urea was also characterized by AFM, which gave similar results. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 471–483, 2009

Block copolymers containing prepolymer segments such as poly(ethylene oxide), poly-(propylene oxide), polybutadiene, and butadiene-styrene copolymer and segments of a vinyl polymer such as styrene and methyl methacrylate were synthesized. A commercially available low-molecular-weight dihydroxyl-terminated prepolymer was reacted with an aliphatic diisocyanate and with 2, 5-dimethyl-2, 5-bis-(hydroperoxy) hexane. The resulting polymeric peroxycarbamates were used as free radical initiators of vinyl polymerization. Various modes of preparation and the properties of the copolymers are described. Formation of block copolymers was illustrated by several characterization methods such as IR spectroscopy, elemental analysis, and elastic modulus versus temperature measurements. The modulation of the mechanical properties of the copolymers with respect to homopolymers was observed and reported by impact strength as well as other certain ASTM properties.

Segmented, nonchain extended polyurethanes and polyureas based on PTMO soft segments (SS) and hard segments (HSs) based on only single molecules of a diisocyanate were synthesized. Type and nature of the diisocyanate was systematically varied in order to analyze the effect of HS symmetry and type of linkage between the HS and SS on the structure‐property relationship of these segmented copolymers. Results showed that the increased symmetry of the diisocyanates allows a more efficient packing of the HSs which leads to a microphase‐separated structure with the crystalline hard ribbon or thread‐like domains percolated throughout the SS matrix, even with a low HS content (ca. 13 wt.%). The service window of these segmented copolymers was significantly influenced by the symmetry and type of linkage between the HS and SS. Most copolymers also showed evidence of strain hardening accented by the strain induced crystallization of the PTMO SS.

Preliminary characterization of amphiphilic segmented copolymers of polydimethylsiloxane and urea ‘hard blocks’ was conducted by measuring isopropyl alcohol (primarily) dilute solution viscosities via capillary viscometry. The traditional data analysis techniques, which provide for extrapolation of intrinsic viscosities from these experiments, revealed that increasing concentrations of polymer produced lower reduced viscosities rather than the expected higher values. A very approximate data fit reveals negative Huggins and Kraemer constants from these analyses, which are highly unusual. In a solvent such as DMF, a similar polymer having poly(tetramethylene oxide) and urea blocks and measured with identical conditions exhibited the expected behavior, showing increasing reduced viscosities over concentrations in the same range. However, the non-linearity of the data is suggestive of much more complex hydrodynamic, or supramolecular, interactions that are not clarified by the initial research.

New novel segmented polyurethane and polyurea copolymers have been synthesized without chain extenders and the structure-property behavior of these systems has been investigated. It is shown that by the proper choice of diisocyanate and its symmetry, one can obtain highly microphase separated systems without chain extenders and that the materials also display useful mechanical behavior. In particular, it is shown that due to the bidentate hydrogen bonding achieved in the segmented ureas, a significant modulus “service temperature window” is also obtained. It is also verified that not only can strong microphase separation be obtained with low weight fraction hard segment content (14%) but that the hard phase, which is comprised of monodisperse “single molecule” units, also displays a percolated thread-like structure throughout the dominant soft segment material — the latter being based on ca. 1000g/mol polytetramethylene oxide.

Novel segmented polyurethaneurea copolymers were synthesized using a poly(ethylene–butylene) glycol based soft segment and either hydrogenated diphenyl methane diisocyanate (HMDI) or hexamethylene diisocyanate (HDI) in addition to either ethylene diamine (EDA) or 2-methyl-1,5-diaminopentane (DY) as the chain extender. Dynamic mechanical analysis (DMA), small angle X-ray scattering (SAXS) and in some cases atomic force microscopy (AFM) established the presence of a microphase-separated structure in which hard microdomains are dispersed throughout a soft segment matrix. Wide angle X-ray scattering (WAXS) and differential scanning calorimetry (DSC) imply that the materials are amorphous. Samples that are made with HMDI/DY and have hard segment contents in the range of 16–23 wt% surprisingly exhibit near-linear mechanical deformation behavior in excess of 600% elongation. They also show very high levels of recoverability even though their hysteresis is also considerable. The materials have all proven to be melt processable in addition to solution processable.

The solid-state structure–property behavior of highly branched segmented poly(urethane urea) (PUU) copolymers and their linear analog was investigated. A limited study of their solution rheological behavior was also undertaken. The linear PUUs were synthesized by the two-step prepolymer method, whereas the oligomeric A2+B3 methodology was utilized to synthesize the highly branched materials. The soft segments (SS) were either poly(tetramethylene oxide) (PTMO) or poly(propylene oxide) (PPO). All copolymers utilized in this study, with one exception, contained 28 wt% hard segment (HS) content. DMA, SAXS, and AFM studies indicated that the linear as well as the highly branched PUUs were microphase separated. The SS Tg of the highly branched PUUs was nearly identical to that of their respective linear analogs. However, the linear copolymers exhibited broader and less temperature sensitive rubbery plateaus, both attributed to one or both of two reasons. The first is better hydrogen bonding organization of the HS phase as well as greater HS lengths than in the highly branched analogs. The second parameter is that of a potentially higher chain entanglement for the linear systems relative to the branched analogs. Tapping-mode AFM phase images confirmed the microphase morphology indicated by SAXS and DMA. Ambient temperature strain-induced crystallization was observed in the PUU based on PTMO 2040 g/mol at a uniaxial strain of ca. 400%, irrespective of the chain architecture. Stress–strain, stress relaxation, and mechanical hysteresis of the highly branched copolymers were in general slightly poorer than that of their linear analogs. Ambient temperature solution viscosity of the highly branched materials in dimethyl formamide was substantially lower that that of the linear samples of nearly equal molecular weight.

The time-dependent morphology development in a segmented polyurethane, which was prepared by the reaction of equimolar amounts of 1,4-phenylene diisocyanate (pPDI) and poly(tetramethylene oxide)glycol of 〈Mn〉 of 975 g/mol, was investigated. No chain extender was utilized during the synthesis, and the resultant monodisperse hard segments constituted 14 wt % of the copolymer. Time-dependent microphase separation and morphology development was studied at room temperature by using solvent-cast films which were heated above the hard segment melting temperature, 55 °C, to erase the semicrystalline microphase morphology. Atomic force microscopy showed that, following heat treatment, the hard phase first developed into short rods within 30 min, followed by a growth period during which the short rods grew longer and eventually into a well-defined percolated structure. Morphology development was also followed by FTIR spectroscopy. While the intensity of the free CO peak at 1730 cm-1 decreased, the intensity of the ...

Poly(propylene oxide) (PPO) was incorporated in a controlled manner between poly(dimethylsiloxane) (PDMS) and urea segments in segmented polyurea copolymers and their solid state structure–property behavior was investigated. The copolymers contained PDMS segments of MW 3200 or 7000 g/mol and an overall hard segment content of 10–35 wt%. PPO segments of MW 450 or 2000 g/mol were utilized. Equivalent polyurea copolymers based on only PDMS as the soft segment (SS) component were used as controls. The materials (with or without PPO) utilized in this study were able to develop microphase morphology as determined from dynamic mechanical analysis (DMA) and small angle X-ray scattering (SAXS). DMA and SAXS results suggested that the ability of the PPO segments to hydrogen bond with the urea segments results in a limited inter-segmental mixing which leads to the formation of a gradient interphase, especially in the PPO-2000 co-SS containing copolymers. DMA also demonstrated that the polyureas based on only PDMS as the SS possessed remarkably broad and nearly temperature insensitive rubbery plateaus that extended up to ca. 175 °C, the upper temperature limit depending upon the PDMS MW. However, the incorporation of PPO resulted in more temperature sensitive rubbery plateaus. A distinct improvement in the Young's modulus, tensile strength, and elongation at break in the PPO-2000 and PDMS-7000 containing copolymers was observed due to inter-segmental hydrogen bonding and the formation of a gradient interphase. However, when PPO was incorporated as the co-SS, the extent of stress relaxation and mechanical hysteresis of the copolymers increased relative to the segmented polyureas based on the utilization of only PDMS as the soft segment component.

Thermoplastic segmented polyurethane and polyurea copolymers whose monodisperse hard segments are based on only a single diisocyanate molecule are discussed. The solid-state structure-property behavior of these materials demonstrates that a proper selection of the level of symmetry and/or cohesiveness of the hard microdomains may allow elimination of the traditional requirement of chain extension to obtain melt processable segmented urethanes, and more specifically, urea copolymers with useful structural properties.

Soluble model segmented poly(urethane urea)s (PUU) with or without hard segment (HS) branching were utilized to explore the importance of hydrogen bonding and chain architecture in mediating the long-range connectivity of the HS phase. The HS content of all the PUU copolymers was 22 wt %, and the soft segment (MW 970 g/mol) was a heterofed random copolymer of 50:50 ethylene oxide:propylene oxide, which possesses a single terminal hydroxyl group (monol). An 80:20 isomeric mixture of 2,4- and 2,6-toluene diisocyanate, 4,4',4''-triphenylmethane triisocyanate and water were utilized during the chain extension step of the synthesis to incorporate HS branching. DSC and SAXS results on the final plaques indicated that the samples were still able to establish a microphase morphology even in the presence of the highest extent of HS branching utilized in the study. The tapping-mode AFM phase image of the PUU sample without HS branching exhibited the presence of long ribbonlike hard domains that percolated through the soft matrix. The long-range connectivity of the HS was increasingly disrupted with higher levels of HS branching. Accompanying such disruption was a systematic mechanical softening of the PUU samples. FT-IR indicated that incorporation of HS branching disrupted the hydrogen-bonded network within the hard phase. These results demonstrate the importance of hydrogen bonding and chain architecture in mediating the long-range connectivity and percolation of the HS and achieving dimensional stability.

The effect of the variables of polydimethylsiloxane (PDMS) soft segment (SS) length, hard segment (HS) type and content as well as choice of chain extender (its MW and symmetry) on the morphology of segmented polyurethane and polyurea copolymers was investigated. The methods of dynamic mechanic analysis, small angle X-ray scattering, atomic force microscopy, and mechanical testing were used in this analysis. Average PDMS MW of 900, 2500 or 7000 g/mol were utilized and the hard segment content ranged from 16 to 50 wt%. HMDI was used as the diisocyanate. All copolymers were synthesized via the prepolymer method. The PDMS MW had a marked effect on the morphology of the materials. Copolymers with PDMS MW of 2500 and 7000 g/mol were clearly found to be well microphase separated relative to those containing the 900 g/mol PDMS SS. The polyurea sample with a PDMS MW of 7000 and HS content of 25 wt% exhibited a remarkable service temperature window (for rubber-like behavior) of ca. 230 °C (from −55 to 175 °C) whereas it was ca. 200 °C wide (from −55 to 145 °C) for the equivalent polyurethane sample. In general, the degree of microphase separation was found to be greater in the polyurea samples due to their more cohesive bidentate hydrogen bonding.

The use of isopropanol (IPA) as the reaction solvent for the preparation of high molecular weight segmented polyether-urea copolymers based on cycloaliphatic diisocyanates was investigated. Reactivity of IPA with bis(4-isocyanatohexyl)methane (HMDI) and isophorone diisocyanate (IPDI) was studied between 0 and 40 °C using in-situ FTIR spectroscopy. HMDI, which has secondary isocyanate groups, shows a very slow reaction with a large excess of IPA at 0 and 23 °C. Analysis of the kinetic data indicates an activation energy of 51 kJ/mol for the reaction between HMDI and IPA. As expected, IPDI, which has both a primary and a secondary isocyanate (NCO) group, reacts faster with IPA compared with HMDI, which only has secondary NCO groups. However, the rate of reaction of IPDI with IPA at 0 °C is extremely slow (approximately 1% consumption of isocyanate in 60 min) thus allowing the use of IPA as the reaction solvent for polyether-urea synthesis. Preparation of high molecular weight, high-strength HMDI and IPDI based polyether-urea segmented copolymers in IPA has been demonstrated. Thermal analysis and stress–strain analyses were used to characterize the products.

Isopropyl alcohol (IPA) is used as the reaction solvent for the preparation of silicone–urea copolymers. Reactivity of isopropanol with bis(4-isocyanatocyclohexyl)methane (HMDI) was investigated at 23 °C using infrared spectroscopy. Spectroscopic studies indicated very low reactivity of IPA towards HMDI at 23 °C. High molecular weight segmented silicone–urea copolymers were prepared through the reaction of HMDI with aminopropyl and N-methylaminopropyl terminated polydimethylsiloxane (PDMS) oligomers and three different chain extenders, ethylene diamine (ED), hexamethylene diamine (HMDA) and 2-methyl-1,5-diaminopentane (Dytek A). Number average molecular weights of PDMS oligomers varied between 900 and 7000 g/mol, respectively. Reactions were carried out at room temperature in IPA. Silicone–urea copolymers with urea hard segment content between 10 and 42% by weight were prepared. Thermal and mechanical characterization of the copolymers indicated the formation of microphase-separated systems with excellent tensile strengths. Interestingly, structure of the diamine chain extender did not show any influence on the mechanical properties of the homologous series of silicone–urea copolymers.

A segmented polyurethaneurea based on poly(tetramethylene oxide)glycol, a cycloaliphatic diisocyanate and an unsymmetrical diamine were prepared. Urea content of the copolymer was 35 wt%. Electrospinning behavior of this elastomeric polyurethaneurea copolymer in solution was studied. The effects of electrical field, temperature, conductivity and viscosity of the solution on the electrospinning process and morphology and property of the fibers obtained were investigated. Results of observations made by optical microscope, atomic force microscope and scanning electron microscope were interpreted and compared with literature data available on the electrospinning behavior of other polymeric systems.

Structure–property relations in polydimethylsiloxane (PDMS) containing segmented copolymers with model hard segments capable of forming hydrogen bonding, such as urea, N-methylurea and urethane have been investigated. High molecular weight silicone containing copolymers with these hard segments were prepared from PDMS oligomers with number average molecular weights ranging from 890 to 3750 g/mol. Due to major differences in the solubility parameters between PDMS and polar hard segments, all copolymers are expected to display good microphase separation. It was demonstrated that mechanical and thermal properties of these copolymers are directly linked to the strength of the hydrogen bonding in the hard segments. As expected, siloxane–urea copolymers displayed much higher tensile strengths when compared with siloxane–N-methylurea and siloxane–urethane copolymers with similar compositions.

Hydrogen bonding in polydimethylsiloxane and polyether based urethane and urea type segmented copolymers was investigated by infrared spectroscopy, differential scanning calorimetry and quantum mechanical calculations. Hydrogen bonding in model urethane and urea compounds was compared with those of the copolymers, in order to determine the extent of interaction and resulting phase mixing between hard and soft segments in these copolymers. Quantum mechanical calculations were also used to determine the interaction energies due to hydrogen bonding in model urethane and urea compounds. Further, similar calculations were also performed to quantify the interactions between silicone and ether type soft segments, and urea and urethane type hard segments. As expected, these calculations clearly indicated the absence of any interaction between silicones and urea groups, while there was substantial hydrogen bonding between urea groups and the oxygen in the ether type soft segments. Results of FTIR studies and quantum mechanical calculations were in good agreement with thermomechanical behavior and mechanical properties of these copolymers.

Transesterification reactions between bisphenol-A polycarbonate and polydimethylsiloxane-polycaprolactone block copolymers were studied in melt at 270°C. Influence of the composition of reaction mixture and the catalyst type on the formation and properties of the products obtained were investigated by spectroscopic, chromatographic and thermal methods. Both of the catalysts used, zinc acetate and lanthanum acetylacetonate are very efficient transesterification catalysts for the system studied. GPC and DSC results clearly show the formation of novel polymers displaying combined properties of the polycarbonate and the silicone-ester copolymer.

High molecular weight segmented polyurethaneurea (PUU) copolymers based on an aliphatic diisocyanate, bis(4-isocyanatocyclohexyl)methane and mixed hydrophilic and hydrophobic soft segments were prepared. Hydrophilic blocks consisted of poly(ethyleneoxide) (PEO) of molecular weight 1450 g/mol, whereas the hydrophobic blocks were poly(tetramethylene oxide) of molecular weight 2000 g/mol. Ethylene diamine was used as the chain extender. Hard segment contents of the copolymers were kept constant at 18%, whereas PEO contents were varied between 0% and 50% by weight. Water vapor permeation rates (WVPR) of thin films (23–178 μm) cast from dimethylformamide solutions were determined. In studies performed at 23°C and 50% relative humidity, the relationship between PEO content and WVPR followed an S-shaped curve. For copolymers containing up to about 15% by weight of PEO, WVPR were fairly low. This was followed by a region where WVPR increased continuously for membranes containing between 15% and 30% PEO. Further increase in PEO content above 30% did not influence the WVPR substantially. There was also a dramatic increase in WVPR with an increase in temperature from 23°C to 37°C. Activation energy of permeation was determined to be 91.5 kJ for PUU containing 22.0% by weight of PEO. Equilibrium water absorption levels of PUU containing different levels of PEO in their backbone structures followed a similar trend to that of WVPR. Hydrophilic PUUs showed good tensile properties and mechanical integrity even at very high levels of water absorption.

Novel fumed silica filled thermoplastic poly(dimethylsiloxane-urea) (TPSU) segmented copolymers were synthesized and characterized. TPSU copolymers were prepared from a cycloaliphatic diisocyanate, aminopropyl terminated PDMS oligomers with number average molecular weights of 3,200, 10,800 and 31,500 g/mol and 2-methyl-1,5-diaminopentane chain extender. Two different types of fumed silica HDK H2000 (hydrophobic) and HDK N20 (hydrophilic) were utilized and incorporated into silicone-urea copolymers in amounts of 1-60% by weight. Influence of the silica type (hydrophilic versus hydrophobic), amount of silica loading and the PDMS soft segment molecular weight on the morphology, tensile properties and modulus-temperature behavior of the nanocomposites were determined. Major observations of this study were: (i) under the blending conditions used, incorporation of silica does not seem to interfere significantly with the hydrogen bonding between urea groups, (ii) incorporation of silica does not affect the glass transition temperature of PDMS, (iii) incorporation of silica influences the tensile and thermomechanical properties of silicone-urea segmented copolymers significantly, (iv) average molecular weight of the PDMS soft segment in the silicone-urea copolymer plays a critical role on the improvement of the tensile properties of the fumed silica/TPSU composites. (C) 2011 Elsevier Ltd. All rights reserved.

Surface properties of polymers play critical roles in many applications. For optimum performance it is desirable to have balanced bulk/surface properties in the resin used. There are various methods for the surface modification of polymeric materials, however, most of them are based on the surface treatment of the finished product. In this paper we try to demonstrate the use of specially designed siloxane containing copolymers as surface modifying additives for various organic polymers. Surface modification is usually achieved by blending small amounts of specific siloxane copolymers into the base resin, which migrate to the surface of the system during processing. As our results and other literature data demonstrate, although siloxanes themselves are inherently hydrophobic, it is possible to obtain hydrophilic segments. Similarly one can attach other organic groups with specific functionalities onto the siloxanes, such as UV stabilizers, flame retardants, etc. in order to improve surface properties of the finished product. There are various factors which influence the kinetics of migration of these additives to the surface. They include the composition, molecular weight and architecture of the siloxane copolymer used, level of additive in blend, method of sample preparation and annealing.

We describe the synthesis and spectroscopic investigation of neodymium-doped silicone-urea copolymers. Absorption and luminescence analysis show that neodymium-doped silicone-urea copolymers are promising candidates for the development of polymer-based active photonic devices in the near infrared.

The principal focus of this review will be to document and discuss the recent developments in the synthesis, properties and applications of polyorganosiloxane containing block, segmented and graft copolymers and network structures. Special emphasis will be given to the synthesis and characterization of reactive, organofunctionally-terminated siloxane oligomers, which are the key starting materials or intermediates in the preparation of these well-defined copolymers. Use of these functionally terminated oligomers in the modification of network structures will be discussed. Detailed descriptions of the copolymer formation reactions and the effect of reaction variables, such as temperature and solvent, on the properties of the resultant materials will be given. Discussions of the bulk and surface morphology of siloxane containing copolymers and their blends with other polymeric systems will be provided. Potential applications of these novel materials and possible future directions in the chemistry and technology of polyorganosiloxane containing polymeric systems will also be discussed.

Siloxane containing copolymers and graft terpolymers are used as compatibilizers for model immiscible polar/non polar blend systems. Compatibilizers generally consisted of a siloxane backbone containing various amounts of polyether and alkyl grafts with controlled molecular weights. Influence of structural and compositional variations and additive concentrations on the interfacial tensions of three, low molecular weight model blend systems, polyolefin/polyether, polypropylene/polyether and polypropylene/polyamide were measured by either the spinning drop or sessile drop methods. Stability of the dispersions and average sizes of the dispersed particles were also determined by optical microscopy. It has been shown that these types of siloxane graft terpolymers were more effective in reducing the interfacial tensions than conventional AB type block systems with no siloxane in their structures. Molecular design and architecture of the siloxane compatibilizers and a proper balance between non-polar and polar grafts played important roles in their efficiencies. Additives with longer siloxane backbone seemed to be more effective in reducing the interfacial tension. In polypropylene/polyether system a linear relationship between the reduction in the interfacial tension and the reduction in the average particle size of the dispersed phase was found. Dispersions formed were very stable even at fairly high processing temperatures.

The structure-property behaviour of new siloxane-urea containing segmented copolymers has been investigated. Amino-propyl terminated poly(dimethylsiloxane) oligomers of from 900–3660 〈 M n 〉 were reacted with various diisocynates to form segmented copolymers with urea linkages. The length of the hard segments in these copolymers corresponds approximately to the length of the diisocynate unit employed. A number of mechanical and thermal properties were investigated for these phase separated materials. It was found that the performance of these copolymers was effected by varying the hard segment type and/or content and that high strength necessitates a microphase texture. The two phase nature of these copolymers was verified by dynamic mechanical, thermal and SAXS studies. The phase separation was found to occur in these copolymers even with 6% hard segment by weight. In conclusion, these materials displayed a behaviour similar to the segmented polyurethanes and were found to be superior to the unfilled silicone elastomers.

Block copolymers containing poly(ethylene oxide) and polystyrene segments were synthesised via chemical reactions. A step-wise procedure was first employed to prepare peroxycarbamates which were later used to initiate free radical polymerization of styrene at elevated temperatures. In some runs the polymerization temperature and time were programmed. Styrene contents, molecular weights, elastic modulus—temperature relationships, impact strengths and stress—strain behaviour of the copolymers were determined.

Preparation de copolymeres trisequences polycaprolactone/PDMS et poly(ethyl-2 oxazoline)/PDMS par copolymerisation de la caprolactone et de l'oxazoline avec les oligomeres telecheliques PDMS comme comonomeres et amorceurs. Mise en evidence par DSC et TMA de leur structure biphasique. Utilisation des copolymeres PCL/PDMS comme additifs modificateurs de surface de polymeres (PET, PMMA, PVC, PU), les melanges obtenus presentant des proprietes de surface hydrophobes

Siloxane-urea copolymers were synthesized from MDI and α, ω-bis(aminopropyl)polydimethylsiloxane of different molecular weights by solution polymerization, using 2-ethoxyethyl ether as the solvent. Chain extenders were also employed in some reactions. Formation of urea linkages were followed by FTIR spectroscopy. The products were characterized by GPC chromatography and intrinsic viscosity measurements. Thermal (DSC) and thermomechanical (TMA) characterization of the products were also carried out. The results indicate the formation of novel, strong multiphase elastomeric siloxane-urea copolymers.

Fluorinated, acrylic vinyl monomers such as; 1H,1H-Heptafluorobutyl acrylate 1 , and 1H,1H-Heptafluorobutyl methacrylate 2 , were copolymerized with sodium-p-styrene sulfonate 3 , via emulsion polymerization. The polymerization reactions were carried out at 70–75°C, for 4.5–5 hours using a water soluble initiator, a nonionic surfactant and a hydrocarbon soluble chain transfer agent. The level of ion-containing monomer was varied between 0–7 mole percent. The copolymers were obtained in high yield and high molecular weight. They showed novel ionomeric behavior as characterized by FTIR, penetration studies, stress-strain tests and DSC.