Influence of soft segment molecular weight on the mechanical hysteresis and set behavior of silicone-urea copolymers with low hard segment contents

Polymer ◽  
2011 ◽  
Vol 52 (2) ◽  
pp. 266-274 ◽  
Author(s):  
Iskender Yilgor ◽  
Tugba Eynur ◽  
Sevilay Bilgin ◽  
Emel Yilgor ◽  
Garth L. Wilkes
Keyword(s):  
Molecular Weight ◽  
Hard Segment ◽  
Soft Segment ◽  
Mechanical Hysteresis

PEG-POSS Hybrid Polyurethanes: Mechanically Robust Nanostructured Hydrogels

2007 ◽  
Vol 1060 ◽  
Author(s):  
Jian Wu ◽  
Qing Ge ◽  
Patrick T Mather
Keyword(s):  
Molecular Weight ◽  
Hard Segment ◽  
Soft Segment ◽  
Phenyl Isocyanate ◽  
Hybrid Network ◽  
Molar Ratio ◽  
Organic Hybrid ◽  
Hybrid Hydrogels ◽  
Hard Segments ◽  
Equilibrium Swelling Ratio

ABSTRACTA series of unique hybrid thermoplastic polyurethanes (TPUs) was synthesized using PEG as soft segment and incorporating an isobutyl-functionalized POSS diol (TMP POSS diol) in the hard segment. The molecular weight of PEG was systematically varied to include 10, 20, and 35 kDa, while the mole ratio of POSS diol (as chain extender) to PEG was in range from 3:1 to 8:1 with samples featuring a PEG molecular weight of 10 kDa. The diisocyanate employed for TPU polymerization was 4,4'-methylenebis(phenyl-isocyanate) (MDI). We found that the hydrophobic hard segments (POSS) can form crystalline structures driven by micro-phase separation, this being due to significant thermodynamic incompatibility between POSS and ethylene oxide units. The POSS nano-crystals thus formed serve as physical crosslinking sites within an inorganic-organic hybrid network. This affords a new hybrid organic-inorganic hydrogel in the water-swollen state. The equilibrium swelling ratio increased monotonically with PEG loading and ranged from ∼70% to ∼600%. The shear modulus, G, of the hybrid hydrogels was observed to span 0.3 < G < 4.0 MPa – C values commonly found for elastomers, not hydrogels. Indeed, the hydrogel stiffness can be finely tuned through the POSS:PEG molar ratio, as this predictably controls swelling in water.

Polyurea Synthesis and Properties as a Function of Hard-Segment Content

1988 ◽  
Vol 61 (1) ◽  
pp. 86-99 ◽  
Author(s):  
Z. S. Chen ◽  
W. P. Yang ◽  
C. W. Macosko
Keyword(s):  
Molecular Weight ◽  
Hard Segment ◽  
Soft Segment ◽  
Tensile Elongation ◽  
Mechanical And Thermal Properties ◽  
Solution Polymerization ◽  
Dynamic Mechanical ◽  
Hard Segment Content ◽  
Mechanical Modulus ◽  
Dynamic Mechanical Modulus

Abstract High-molecular-weight linear polyureas of different hard-segment content are obtained with a two-step solution polymerization. Elimination of water, careful choice of solvent, reactant concentration, and good control of reaction temperature are essential to obtain satisfactory results. We have studied the influence of the hard-segment content on the mechanical, dynamic-mechanical, and thermal properties of these solution polymerized amine-terminated polypropylene-oxide-based thermoplastic polyureas. Two-phase morphology is predominant within the range of the hard-segment concentration studied. Inversion of the continuous and dispersed phase might occur in the polyurea series at about 60 wt.% of hard segment. This changes the nature of the polyureas from a tough elastomeric material to a more brittle, high-modulus plastic. The modulus of the rubbery plateau measured from dynamic-mechanical spectra increases with hard-segment concentration due to the reinforcing effect of hard-segment domains. However, continuous improvement in dynamic-mechanical modulus is not significant when the hard segment is above 50 wt.% due to higher degree of phase mixing in high hard-segment concentration systems. The amount of solubilized hard segment in the soft-segment phase in these polyureas is limited as judged from the relatively constant soft-segment Tg. However, the extent of phase separation, as determined by the heat capacity change ΔCp across the soft-segment Tg, decreases with increasing hard-segment content. The same characterizations and analyses have also been carried out on a series of RIM produced polyurea samples of the same composition. Great difference in properties is observed in comparison of these two sets of samples due to their different synthesis routes. In general, samples produced by RIM exhibit lower molecular weight, lower dynamic-mechanical modulus, higher soft-segment Tg, more phase-mixed, and more tensile elongation than those synthesized by solution polymerization. The detailed comparison will be treated in a separate paper.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

scholarly journals Effect of DMPA and Molecular Weight of Polyethylene Glycol on Water-Soluble Polyurethane

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1915 ◽  
Author(s):  
Eyob Wondu ◽  
Hyun Woo Oh ◽  
Jooheon Kim
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Polyethylene Glycol ◽  
Photoelectron Spectroscopy ◽  
Water Solubility ◽  
Soft Segment ◽  
Water Soluble ◽  
Size Exclusion ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry

In this study water-soluble polyurethane (WSPU) was synthesized from isophorone diisocyanate (IPDI), and polyethylene glycol (PEG), 2-bis(hydroxymethyl) propionic acid or dimethylolpropionic acid (DMPA), butane-1,4-diol (BD), and triethylamine (TEA) using an acetone process. The water solubility was investigated by solubilizing the polymer in water and measuring the contact angle and the results indicated that water solubility and contact angle tendency were increased as the molecular weight of the soft segment decreased, the amount of emulsifier was increased, and soft segment to hard segment ratio was lower. The contact angle of samples without emulsifier was greater than 87°, while that of with emulsifier was less than 67°, indicating a shift from highly hydrophobic to hydrophilic. The WSPU was also analyzed using Fourier transform infrared spectroscopy (FT-IR) to identify the absorption of functional groups and further checked by X-ray photoelectron spectroscopy (XPS). The molecular weight of WSPU was measured using size-exclusion chromatography (SEC). The structure of the WSPU was confirmed by nuclear magnetic resonance spectroscopy (NMR). The thermal properties of WSPU were analyzed using thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).

Effect of Catalysts on the Properties of Fluorinated Polyurethanes

2013 ◽  
Vol 464 ◽  
pp. 9-13 ◽  
Author(s):  
Zan Li ◽  
Xia Wang ◽  
Ying Li ◽  
Wei Chain ◽  
Jiao Jiao Hu
Keyword(s):  
Hard Segment ◽  
Soft Segment ◽  
Force Microscopy ◽  
Atomic Force ◽  
Structure Surface ◽  
Improved Stability ◽  
Ft Ir ◽  
Tin Metal ◽  
Polyether Polyol ◽  
Catalyst Efficiency

Fluorinated polyurethanes (FPU) was prepared using fluorinated polyether polyol (FPO) as the soft segment, 4,4`-diphenylmethane diisocyanate (MDI) as the hard segment, 1,4-butanodiol (BDO) as the chain extender and catalysts. Tin metal catalysts were used to catalyze the polyurethane reaction of polyether polyols and isocyanate. The effect of different catalysts including stannous octoate (T-9) and dibutyltindalautrate (DBTDL) on the structure, surface properties and thermal properties of FPU was studied. The structural elucidation of the synthesized FPU was performed by Fourier transform infrared (FT-IR) and discovered that with decreasing catalyst efficiency or without catalyst, the strength of hydrogen bounds were enhanced. The FPU films surface was characterized by contact angle (CA) and atomic force microscopy (AFM) and it was found that the phase separation was increasing with increasing catalyst efficiency. The thermal property was exhibited by Thermo gravimetric (TG) and showed that joining catalyst improved stability significantly.

Effect of Block Molecular Weight on the Mechanical Properties of PA1010-b-PEG Segmented Block Copolymers

2012 ◽  
Vol 512-515 ◽  
pp. 2127-2130
Author(s):  
Li Huo ◽  
Cai Xia Dong
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Block Copolymers ◽  
Microphase Separation ◽  
Soft Segment ◽  
Mechanical Measurements ◽  
Wide Range ◽  
Hard Block ◽  
Higher Temperature ◽  
Hard Segments

The mechanical properties were investigated of a series of PA-PEG thermalplastic elastomer based on PA1010 and polytetramethylene glycol (PEG) with varying hard and soft segment content. Dynamic mechanical measurements of these polymers have carried out over a wide range of temperatures. The block copolymers exhibit three peaks, designated as α, β and γ in the tanδ-temperature curve. The α transition shifts to higher temperature with increasing hard block molecular weight. However, at a constant hard molecular weight, the α transition shifts to higher temperature and the damping increases on increasing the soft segment molecular weight. DMA results show that the block copolymers exhibit a microphase separation structure and both soft and hard segments were found to be crystallizable. The degree of phase separation increases with increasing hard block molecular weight.

Engineering of endothelial cell response on biphasic polyurethane matrix

TECHNOLOGY ◽  
2016 ◽  
Vol 04 (03) ◽  
pp. 139-151 ◽  
Author(s):  
Yuan Yuan ◽  
Calvin Cheah ◽  
Ayesha Arzumand ◽  
Jing Luo ◽  
G. Rajesh Krishnan ◽  
...  
Keyword(s):  
Endothelial Cell ◽  
Cellular Response ◽  
Hard Segment ◽  
Soft Segment ◽  
Hexamethylene Diisocyanate ◽  
Cell Matrix ◽  
Endothelial Cell Response ◽  
Cell Matrix Interactions ◽  
Poly Caprolactone ◽  
Cell Cell

Polyurethanes (PUs) are composed of soft and hard segments, and segmental interactions induce biphasic morphologies which can influence endothelial cell (EC) organization by regulating cell–matrix and cell–cell interactions. In this study, we explored this effect using poly(caprolactone) (PCL)-based PU, where the soft segment was composed of PCL and the hard segment was composed of hexamethylene diisocyanate (HDI) and L-tyrosine-based dipeptide (DTH). The composition of the PUs was varied by altering the PCL molecular weight and correspondingly, different phase morphologies were observed. Organization and functional state of ECs on these PUs showed that composition and phase morphology of PU have a significant effect on cellular response. The ECs formed an organized network with cord-like structures which resulted in interconnected loops when soft and hard segment fractions were phase-separated. VE-cadherin (for cell–cell adherence) and vinculin (for cell–matrix focal adhesion) localized at the tip of interconnecting cells in the tube structures indicated synchronized cell–cell and cell–matrix interactions.

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