Waterborne polysiloxane–urethane–urea for potential marine coatings

Bulk, surface and blood-contacting properties of polyether polyurethanes modified with polydimetnylsiloxane macroglycols

Much attention has been focused on the development of a new type of bioactive material with mechanical properties analogous to those of natural bone. The present authors previously showed that some polydimethylsiloxane (PDMS)-modified CaO–SiO2–TiO2 hybrids prepared by sol-gel method show apatite-forming ability in a simulated body fluid (SBF), which is indicative of bioactivity. In the present study, effects of composition of PDMS-modified CaO–SiO2–TiO2 hybrids on their bioactivity and mechanical properties were investigated. The bioactivity of the hybrids increased with decreasing PDMS content and increasing TiO2 content. Their strain at failure increased with increasing PDMS content and decreasing TiO2 content. Some samples showed high bioactivity, as well as analogous mechanical properties to those of human cancellous bones. This type of hybrids might be useful as a bone-repairing material.

A liquid crystalline polysiloxane (LCP), having an ether bond in the spacer between its siloxane main chain and its mesogenic-group side chains, exhibited a very small electrorheological (ER) effect or increase in shear stress upon application of an electric field, but mixtures of the LCP and polydimethylsiloxane (PDMS) exhibited a sharply increasing ER effect with increasing PDMS content throughout the tested range of up to 0.5 of PDMS weight fraction. When phenyl-substituted PDMS (Ph-PDMS) at a weight fraction of 0.3 was used instead of PDMS, however, the ER effect decreased with increasing phenyl content and became nearly undetectable with Ph-PDMS having a phenyl content (ratio of substituted phenyl groups to initial methyl groups) of approximately 15%. DSC analyses showed that the ER effect of the LCP/PDMS mixtures occurred undiminished throughout a temperature range in which LCP itself is an isotropic liquid in the absence of an applied electric field and suggested that the LC structure of the LCP was maintained even when it was diluted with PDMS in weight fractions of 0.5 or higher, but disrupted when diluted by a 0.3 weight fraction of Ph-PDMS having a 15% phenyl content. Optical microscopic observation of the mixtures of the LCP with a 0.3 weight fraction of PDMS or Ph-PDMS (15% phenyl content) showed that both consisted of uniformly dispersed micron-sized droplets which became elongated in the direction of the applied electric field when it was applied alone but became smaller when both the electric field and shear were applied. These results suggest that the phase separation between the LCP and the dilution oil, as well as the existence and orientation of LC domains, is essential for the generation of a large ER effect. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1319–1328, 1997

Effect of intersegmental interactions on the morphology of segmented polyurethanes with mixed soft segments: A coarse-grained simulation study

A series of siloxane modified waterborne polyurethanes (SWPUs) were synthesized using poly (tetramethylene oxide glycol) (PTMG, 2000 g/mol), hydroxy-terminated poly(dimethylsiloxane) (PDMS, 110,000 g/mol), isophorone diisocyanate (IPDI), 2,2-bis-(hydroxymethyl) propionic acid (DMPA), triethylamine (TEA) and ethylenediamine (EDA). The structure of the prepared SWPU films were examined and confirmed by Fourier transform infrared spectroscopy (FT-IR). The effects of PDMS content on the thermal properties of siloxane modified waterborne polyurethane (SWPUs) were investigated.

The relationships between the properties and microstructures of two series of perfectly alternating bisphenol A-polycarbonate-polydimethylsiloxane block copolymers were studied. In the first series, the polycarbonate (PC) block length was kept constant while the block length of polydimethylsiloxane (PDMS) was varied. The tensile properties of these block copolymers were found to be a function of composition. Dynamic mechanical properties measured as a function of temperature revealed the two-phase nature of these materials. Transmission electron micrographs showed that all samples had a sponge-like morphology independent of composition. The rheological maximum viscosity for the sample containing PC and PDMS blocks of equal molecular weight and extrudate swells increased with PC content. Takayamagi's mechanical coupling model was used to predict the maximum loss tangent at the glass transition temperature of PDMS using the known properties of pure components. The predictions agreed fairly well with the experimental results. In a second series of block copolymers, the block molecular weights of both PC and PDMS were varied to keep the composition constant. The tensile strength of these samples was found to increase with block molecular weights, except for the sample having the highest block molecular weights. The lower tensile strength of this material was attributed to its lamellar type morphology. Cold crystallization of PDMS blocks was found for samples having high PDMS block molecular weight (greater than 8000 g/mole). The Tg of PC blocks followed the Fox-Flory equation with a higher K value than expected. The PDMS content in PC domains was calculated to range from 11% for material of low block molecular weights to about 1.3% for high block molecular weight material.

A material-guided, regenerative approach to heal cranial defects requires a scaffold that cannot only achieve conformal fit into irregular geometries but also has bioactivity and suitable resorption rates. We have previously reported "self-fitting" shape-memory polymer (SMP) scaffolds based on poly(ε-caprolactone) diacrylate (PCL-DA) that shape recover to fill irregular defect geometries. However, PCL-DA scaffolds lack innate bioactivity and degrade very slowly. Polydimethylsiloxane (PDMS) has been shown to impart innate bioactivity and modify degradation rates when combined with organic cross-linked networks. Thus, this work reports the introduction of PDMS segments to form PCL/PDMS SMP scaffolds. These were prepared as co-matrices with three types of macromers to systematically alter PDMS content and cross-link density. Specifically, PCL90-DA was combined with linear-PDMS66-dimethacrylate (DMA) or 4-armed star-PDMS66-tetramethacrylate (TMA) macromers at 90:10, 75:25, and 60:40 wt % ratios. Additionally, a triblock macromer (AcO-PCL45-b-PDMS66-b-PCL45-OAc), having a 65:35 wt % ratio PCL/PDMS, was used. Scaffolds exhibited pore interconnectivity and uniform pore sizes and further maintained excellent shape-memory behavior. Degradation rates increased with PDMS content and reduced cross-link density, with phase separation contributing to this effect. Irrespective of PDMS content, all PCL/PDMS scaffolds exhibited the formation of carbonated hydroxyapatite (HAp) following exposure to simulated body fluid (SBF). While inclusion of PDMS expectedly reduced scaffold modulus and strength, mineralization increased these properties and, in some cases, to values exceeding or similar to the PCL-DA, which did not mineralize.

Functionalization of polyurethanes by incorporation of alkyne side-groups to oligodiols and subsequent thiol–yne post-modification

Since A. Fick had observed different transport of gas molecules through nitro-cellulose, membrane-based gas separation has been extensively studied for membrane materials as well as scale-up and application to industrial gas separation field. Numerous scientists have studied the transport mechanism, measurement of gas permeation, membrane materials, and high flux membrane by asymmetric fabrication.Acknowledged to the contribution for quantative measurement of gas permeabilities by H. A. Daynes and R. M. Barrer, a number of materials have been tested and applied for gas separation membranes: polydimethylsiloxane (PDMS), cellulose acetate (CA), polysulfone (PSf), polyethersulfone (PES), and polyimide (PI), etc. PDMS, a kind of highly permeable polymer, has been used in VOCs recovery due to its superior sorption capacitance. CA and fluorinated polyimides have been employed to natural gas calorie-up process and petrochemical industries while PES and PSf have been mainly used for nitrogen enrichment from air.In a dense polymer film, gas permeation through the membrane depends upon both sorption and diffusion known as ‘solution-diffusion’ mechanism proposed by Sir Thomas Graham at 1866. Sorption, a thermodynamic factor, is occurred when a gas molecule in bulk motion adsorb physically on a membrane surface with respect to the concentration difference, and diffusion, a kinetic factor, is related to the extent how fast a gas molecule go through the membrane. Therefore, two factors are simultaneously crucial for efficient permeation and separation.While the conventional polymer membranes exhibited somewhat low permeation and selective performances, along with the recent developments in materials science, recently reported membrane materials showed excellent permeability and selectivity for various gas pairs as well as enhanced thermal, chemical and mechanical stabilities. The recent polymer membranes can be classified largely into two classes; highly diffusive membranes due to their high free volume elements and sorption-enhanced membranes based on high sorption capacity on carbon dioxide and hydrocarbons.Glassy polymers possessing rigid structure and strong intermolecular forces have been generally known to show reduced gas permeabilities although low diffusion through the membrane enabled to separate gas molecules efficiently resulting in high diffusion selectivity. However, superglassy polymers containing distorted structure and the resulting increased free volume elements (FVE) were developed since T. Matsuda et al. reported extraordinarily permeable glassy polymer, poly[1-(trimethylsilyl)-1-propyne](PTMSP). Since PTMSP was developed in 1983, acetylene-based polymers such as poly(4-methyl-2-pentene)(PMP), poly(1-phenyl-1-propyne)(PPP) have been followed by the introduction of various substitution groups. Extraordinarily high permeabilities, for example, 9,700 Barrer of oxygen permeability for PTMSP, were obtained from these acetylene-based polymers, while the separation performances were not successful because of their relatively large FVE size for separation. Fluorinated polymers, famous as the commercial names like AF 1600, AF 2400, Hyflon AD and Cytop, are candidate polymers for gas separation as well. Recent development of polymers with intrinsic microporosities (PIMs) showed competitive performances resulted from the intrinsic FVE due to the bulky and distorted structures. Thermally rearranged (TR) polymer membranes also presented optimized performances for gas separation. Chain rearrangement at the solid state improved the FVE in the polymer matrix followed by superior permselectivities as well as high permeabilities.Sorption-enhanced polymer membranes are beneficial to obtain superior permeability as well as advanced selectivity especially for carbon dioxide, hydrocarbons and VOCs because condensable gas molecules are easier to be adsorbed on the polymer surface. Recent researches are focused on the usage of ethylene oxide group, which has unique interaction with quadrupole monetum of carbon dioxide. From poly(dimethyl siloxane)(PDMS), the original sorption-based polymer, poly(ethylene oxide)(PEO), crosslinked PEO, PEO-based block copolymers such as poly(ethylene oxide-b-amide)(Pebax), poly(ethylene oxide-b-ethylene terephthalate)(PEO-b-PET) will be discussed from the viewpoint of permeabilities, solubilities and also their temperature dependences.In this book chapter, the chemical structure, physical properties, gas permeabilities and selectivities will be surveyed on the focus of up-to-date high performance and higly permeable membranes for gas separation.

ABSTRACTNylon-6-b-polydimethylsiloxane copolymer was synthesized with macroinitiator through in situ polymerization. The macroinitiator with two chain-growing centers per molecule is based on hydroxyl terminated polydimethylsiloxane (PDMS) functionalized with diisocyanate. The influence of PDMS contents on the properties of copolymers was studied. Differential scanning calorimetry and X-ray diffraction were used to investigate the melting temperature, crystallization temperature and crystal form of samples, and the results showed that the crystallinity of polymers decreased. The mechanical properties of samples were studied by notched-impact testing and tension test. The notched impact strength was improved by 200% with PDMS concentration up to 4 wt%. The form of scaly was seen by scanning electron microscope proved the improvements of the impact strength of the copolymer. The water contact angles test showed that the surface tension of copolymers decreased with the PDMS content increasing and the surface of copolymer changed from hydrophilic to hydrophobic.

Huge quantities of chrome-tanned leather wastes are produced every year from leather, footwear and clothing related industries. Many attempts have been made to reuse them in the form of boards, sheets, composites, etc. However, most of those methods have deficiencies such as low flexibility, cost effectiveness, non-eco-friendly, stringent process control and unacceptable properties. Our current work relies on an alternate method of reusing these wastes to form composite sheets with desirable characteristics. The waste chrome shavings were partially hydrolyzed and made into composite sheets using an eco-friendly polydimethylsiloxane (PDMS) polymer. The sheets were characterized for their mechanical, thermal and morphological properties. The tensile and thermal properties of composite sheets increase gradually upon increase in PDMS concentration up to 20 wt.% followed by an abrupt decrease when the PDMS concentration increased further to 30 and 40 wt.%. The softness of sheets has an inverse relationship with tensile stress and directly proportional to the elongation values. Fourier-transformed infrared (FTIR) analysis of composite sheets revealed the presence of dominant peaks corresponding to amide bands of collagen as well as characteristic bands of PDMS, showing the homogeneity of the developed composite sheets. Thus the developed composite sheets demonstrate potential for numerous applications in footwear, clothing and related industries.

Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on α-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether-urethane-urea)s (PEUUs) was synthesized via direct reaction of 4,4'-methylene-bis(4-phenylisocyanate) (MDI), L-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized.

To treat coal gasification wastewater containing phenol, polydimethylsiloxane (PDMS)/polyvinylidene fluoride (PVDF) hollow fiber composite membrane was made by dynamic negative pressure coating method, using PVDF hollow fiber membrane as base membrane, PDMS as modifying membrane material, to improve pervaporation performance of PDMS by the cross-linking modification. The influence of cross-linking agent, PDMS concentration, coating time on pervaporation performance of the composite membrane was investigated. Actual coal chemical wastewater with phenol concentration 1600-1800 mg/L, COD 13000-15000 mg/L was treated by the obtained PDMS/PVDF composite membrane, and at temperature 70℃, the flow rate of 10 L/h, pressure under membrane 3KPa, phenol flux 16.81 g/(m2·h), separation factor reaches 8.103.

Partial crystalline organosilicon-based polysiloxane-polyurethane copolymers

SiOC ceramic microparts and patterned microstructures are fabricated from their metal masters using polysiloxanes as a precursor, which consists of polyhydromethylsiloxane (PHMS) and 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetrasiloxane (D 4 Vi), via mold transfer, liquid cast, crosslink, and pyrolysis. The mixed liquid of PHMS and D 4 V was cast with the polydimethylsiloxane (PDMS) negative molds transferred from the masters and solidified via hydrosilylation of PHMS and D 4 Vi under controlled heating. Because both the precursors and mold materials are polysiloxanes, their chemical similarities ensure the excellent contact between the two phases that allows for the precise duplication of the master microstructures into the polysiloxanes. Strategies were developed for the use of a two‐step controlled heating method and the use of polysiloxane as a support in the processes of demolding, crosslinking, and pyrolysis in order to ensure the bonding qualities of both the crosslinked bodies and the pyrolyzed microstructures. Through this route, we obtained dense and crack‐free SiOC ceramic microngears and arrayed holes of well‐duplicated microstructures with a resolution down to the submicrometers. Moreover, the polysiloxanes allow the direct imprints with the metal masters to form inversed microstructures of SiOC ceramics, as demonstrated by the formation of microchannels and various motifs of SiOC ceramics from their metal counterparts.