Polyurethanes with aggregation-enhanced emission characteristics: preparation and properties

2017 ◽  
Vol 196 ◽  
pp. 43-54 ◽  
Author(s):  
Kun Wang ◽  
Jiping Yang ◽  
Chen Gong ◽  
Hao Lu
Keyword(s):  
Fluorescence Intensity ◽  
Soft Segment ◽  
Fluorescence Emission ◽  
Water Mixture ◽  
Stimuli Responsive ◽  
Scanning Calorimetry ◽  
Responsive Materials ◽  
Molar Ratios ◽  
Soft Segments ◽  
Hard Segments

An amino-terminated poly(propylene glycol)-modified tetraaryl-buta-1,3-diene derivative (TABDAA) was introduced to synthesize polyurethanes with different ratios of soft/hard segments. A mixture of TABDAA and poly(tetrahydrofuran) 1000 as the soft segments was reacted with 4,4-diphenylmethane diisocyanate and 1,4-butanediol as the hard segments in molar ratios of 1 : 2 : 1, 2 : 3 : 1, and 3 : 4 : 1 to give the desired polyurethanes named TMPU-211, TMPU-321 and TMPU-431, respectively. The three polyurethanes exhibited different aggregation-enhanced emission (AEE) behaviors because of their different soft/hard segment ratios. The polyurethanes with a higher soft segment content tended to form bigger particles in a DMF/water mixture solution, thus causing a sharper increase in their fluorescence intensity. In addition, the polyurethane films exhibited different fluorescence intensities after different heat treatments. After a quenching treatment of the soft segments in the polyurethane films, the fluorescence intensity dropped greatly. When these quenched polyurethane films were thermally annealed at 60 °C for 24 hours, their fluorescence intensity exceeded the initial intensity of the as-prepared films. Differential scanning calorimetry results showed that the polyurethane films in the quenched condition did not present the endothermal melting peak of the soft segments, and the melting peaks appeared again after thermal annealing. AFM experiments showed that an ordered arrangement was achieved after the heat treatment of these AEE polyurethane films. These results demonstrated that the polymer structure had a significant effect on the AEE properties of the polyurethane films, and more importantly, it is of great significance in improving the fluorescence emission of the AEE polymers and also for their potential application in fluorescent probes, stimuli-responsive materials, PLED devices and so on.

Systematic evaluation of pH and thermoresponsive poly(n-isopropylacrylamide-chitosan-fluorescein) microgel

e-Polymers ◽  
2017 ◽  
Vol 17 (5) ◽  
pp. 399-408 ◽  
Author(s):  
Pedro Hernández ◽  
Armando Lucero-Acuña ◽  
Cindy Alejandra Gutiérrez-Valenzuela ◽  
Ramón Moreno ◽  
Reynaldo Esquivel
Keyword(s):  
Biomedical Application ◽  
Systematic Evaluation ◽  
Molar Ratio ◽  
Solution Temperature ◽  
Stimuli Responsive ◽  
Scanning Calorimetry ◽  
Molar Ratios ◽  
Stimuli Responsive Polymers ◽  
Wide Range ◽  
Low Molecular Weight Chitosan

AbstractThe interesting properties of stimuli-responsive polymers lead to a wide range of possibilities in design and engineering of functional material for the biomedical application. A systematic approach focused on the evaluation of the physical properties of multiresponse (pH and temperature) PNIPAM was reported in this work. The effect of three different molar ratios of poly(n-isopropylacrylamide): chitosan (1:49, 1:99 and 1:198) were evaluated and labeled correspondingly as PC1F, PC2F, and PC3F. An increase in the lower critical solution temperature (LCST) of sample PC1F (34°C) was observed by differential scanning calorimetry (DSC). The presence of low molecular weight chitosan (LMWC) full-interpenetrating polymer (Full-IPN) segments in poly(n-isopropylacrylamide) was confirmed by Fourier-transform infrared spectroscopy (FT-IR). The hydrogel’s water capture was analyzed by two models of swelling, the power law model and a model that considers the relaxation of polymeric chains of the hydrogel, finding good correlations with experimental data in both cases. Sample PC3F resulted with higher swellability, increasing the weight of the hydrogel around seven times. Hydrogel pH-sensibility was confirmed placing the samples at different pH environments, with an apparent increase in swellability for acidic conditions, confirming the highest swellability for sample PC3F, due to hydrogen bonds boosted by chitosan high molar ratio. Based on these results, the hydrogel obtained has potential as a thermo-pH triggered hydrogel in drug delivery applications.

scholarly journals The effect of the polar solvents on the synthesis of poly(urethane-urea-siloxane)s

2012 ◽  
Vol 77 (10) ◽  
pp. 1457-1481 ◽  
Author(s):  
Milica Balaban ◽  
Vesna Antic ◽  
Marija Pergal ◽  
Iolanda Francolini ◽  
Andrea Martinelli ◽  
...  
Keyword(s):  
Monomer Concentration ◽  
Gel Permeation Chromatography ◽  
Molar Ratio ◽  
Solvent Ratio ◽  
Solvent Mixtures ◽  
Scanning Calorimetry ◽  
Experimental Conditions ◽  
Water Contact ◽  
Soft Segments ◽  
Hard Segments

Segmented poly(urethane-urea-siloxanes) (PUUS) based on 4,4?- methylene diphenyl diisocyanate-ethylene diamine (MDI-ED) hard segments and hidroxypropyl-terminated poly(dimethylsiloxane) (PDMS, M n =1000 g mol-1) soft segments were prepared under various experimental conditions. The copolymers with constant molar ratio of hard and soft segments (PDMS:MDI:ED = 1:2:1; 20 wt. % of the hard segments) were synthesized in two different solvent mixtures, by two-step polyaddition procedure. The first one was THF/DMAc with different co-solvent ratio (1/1, 1/2 and 1/9, v/v), whereas the second one was THF/NMP (1/9, v/v). The reaction conditions were optimized by varying the co-solvents ratio, the concentration of the catalyst, the initial monomer concentration, as well as the time of the first and the second step of reaction. The effect of the experimental conditions on the size of PUUS was investigated by gel permeation chromatography (GPC) and viscometry of the dilute solutions [?]. The copolymers with the highest molecular weights were obtained in the THF/NMP mixture (1/9, v/v). The structure and composition of the copolymers were determined by 1H NMR and FTIR spectroscopy. The morphology of the synthesized copolymers was investigated by atomic force microscopy (AFM), while the thermal properties were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The surface properties were evaluated by measuring the water contact angle (WCA). The copolymers showed phase separated microstructure and were stable up to 200?C in nitrogen.

scholarly journals Synthesis, structure and properties of thermoplastic poly(ester-siloxane) elastomers

2006 ◽  
Vol 71 (7) ◽  
pp. 839-842
Author(s):  
Vesna Antic ◽  
Jasna Djonlagic
Keyword(s):  
1H Nmr Spectroscopy ◽  
Mechanical Analysis ◽  
Structure And Properties ◽  
Mass Ratio ◽  
Scanning Calorimetry ◽  
Constant Length ◽  
Melting Temperatures ◽  
Soft Segments ◽  
In Series ◽  
Hard Segments

Two series of thermoplastic poly(ester-siloxane) elastomers (TPES), with hard segments based on poly(butylene terephthalate) (PBT) and soft segments based on poly(dimethylsiloxane) (PDMS), were synthesized by high-temperature two-step transesterification reaction in the melt. In series I, the mass ratio of hard and soft segments was kept constant (57:43), while the length of the segments was varied, whereas in series II, the mass ratio of hard and soft segments was varied in range from 70:30 to 40:60, with a constant length of the soft segments. The segmented structure of the poly(ester-siloxane) copolymers was verified by 1H-NMR spectroscopy of the soluble and insoluble fractions, obtained after extraction of the samples with chloroform. The influence of the structure and composition of the TPES on the melting temperatures and degrees of crystallinity was investigated by differential scanning calorimetry (DSC). The rheological properties were investigated by dynamic mechanical analysis (DMA).

Gelation of thermoplastic polyurethane/2-butanone solutions

e-Polymers ◽  
2005 ◽  
Vol 5 (1) ◽  
Author(s):  
Sonia Florez ◽  
María Eugenia Muñoz ◽  
Anton Santamaría
Keyword(s):  
Hard Segment ◽  
Critical Concentration ◽  
Thermoplastic Polyurethane ◽  
Crystallization Rate ◽  
Solution Viscosity ◽  
Scanning Calorimetry ◽  
Soft Segments ◽  
Gelation Concentration ◽  
Hard Segments ◽  
Chain Entanglements

AbstractNew features of thermoplastic polyurethane (PUR)/2-butanone gels are investigated, using dynamic viscoelastic measurements and differential scanning calorimetry. The work is focused on the effect of the hard-segments content on the gelation process. In the case of PUR with the highest hard-segment fraction (30%), soft segments are not able to crystallize on cooling from solution; consequently, gels are not formed. The copolymer with the lowest hard-segment content (12%) gives the shortest gel times. This is attributed to the low solution viscosity of this copolymer, which enhances the crystallization rate. All gels melt at 7°C, giving rise to a viscoelastic solution in a thermoreversible process. The critical gelation concentration is below the critical concentration for polymer chain entanglements.

Chain Conformation in Elastomeric Multiblock Copolymers as Measured by Small-Angle Neutron Scattering

1985 ◽  
Vol 58 (5) ◽  
pp. 899-912 ◽  
Author(s):  
Stuart L. Cooper ◽  
John A. Miller
Keyword(s):  
Small Angle ◽  
Hard Segment ◽  
Elevated Temperatures ◽  
Soft Segment ◽  
Random Coil ◽  
Radius Of Gyration ◽  
Soft Phase ◽  
Soft Segments ◽  
Hard Segments ◽  
Increasing Temperature

Abstract Small-angle neutron scattering has been shown to be an effective technique for investigating segment conformation in two-phase multiblock copolymer systems. By choosing the appropriate isotopic compositions, either segment can be investigated, as can the whole chain. The best approach to the experiment is to use a phase-contrast matched sample, one where no interphase scattering occurs. This allows the experiments to be carried out on a single sample, simplifying the experiment, and reducing the beam time requirements. Equations (2) and (3) describe the phase-contrast matched criterion. At room temperature, the polyether soft segments in the polyurethane elastomer-and in the polyether-polyester block copolymers are somewhat extended on the average relative to the bulk oligomer conformation. In the polyether-polyester with a lower hard-segment content, the soft segments are less extended than in the higher ester content material. A distribution of conformations occurs in these materials, with a majority of the soft segments being nearly in a random-coil conformation. A substantial number of segments are fairly taut, leading to an average conformation that is somewhat extended relative to the random coil conformation. The soft-segment radius of gyration in the polyurethane material initially decreases with increasing temperature. As the temperature rises, the retractive force on the taut soft segments increases, thus facilitating the extraction of hard segments from the amorphous hard phase into the soft phase. One would expect that the degree of phase separation would decrease with increasing temperature due to such a mechanism, and in fact this is borne out by small-angle x-ray scattering studies. Above 150°C, an upturn in the soft-segment radius of gyration is observed. Koberstein et al. propose a phase mixing transition around this temperature in polyurethane systems. Such a transition implies a greater compatibility between the hard and soft segment types at elevated temperatures. Thus, a swelling of the soft segments is seen due to favorable interactions with the hard segments located in the soft phase. A schematic diagram of the polyurethane microstructure and chain conformation is presented in Figure 9. The soft-segment radius of gyration in the polyether-polyester materials decreases smoothly with increasing temperature. This is primarily due to a decrease in the number of taut tie molecules present at elevated temperatures due to the rearrangement of the hard crystalline domains. In addition, relaxation of stresses introduced by molding these samples below the hard-segment crystalline melting temperature may contribute to the decrease in the soft-segment Rg.

Diacetylene Containing Polyesters and Segmented Polyurethanes with Body Temperature Sensitive Thermochromic Transitions

1993 ◽  
Vol 328 ◽  
Author(s):  
Ken D. Zemach ◽  
M. F. Rubner
Keyword(s):  
Body Temperature ◽  
Soft Segment ◽  
Polymerization Process ◽  
Temperature Sensitive ◽  
Processing Conditions ◽  
Highly Sensitive ◽  
Wide Range ◽  
Soft Segments ◽  
Hard Segments ◽  
Segmented Polyurethanes

ABSTRACTSeveral diacetylene containing polyesters with thermochromic transitions at or around room temperature have been synthesized. Some of these polymers have been shown to be highly sensitive to body temperature, giving rise to either reversible or irreversible thermochromic changes, depending upon both the molecular structure and the processing conditions. By changing the structure and processing conditions, the thermochromic transition can be moved over a wide range of temperatures. Segmented polyurethanes using these diacetylene functionalized polyesters as soft segments and containing diacetylene groups in the hard segments have also been produced. Through a selective polymerization process, it is possible to selectively cross-polymerize the hard segment diacetylene groups or cross-polymerize both the hard and soft segments thereby making it possible to examine the effects of hard and soft segment crosslinking on mechanical properties.

HVEM and high resolution SEM of polyurethane bulk and surface structure

1988 ◽  
Vol 46 ◽  
pp. 936-937
Author(s):  
S. L. Goodman ◽  
C. Li ◽  
S. L. Cooper ◽  
R. M. Albrecht
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Soft Segment ◽  
Structure Property ◽  
Two Phase ◽  
Near Surface ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Soft Segments ◽  
Hard Segments

Segmented polyurethanes (PUs) are composed of alternating blocks of crystalline or glassy urethane “hard segments” and rubbery “soft segments.” Chemical incompatability between hard segment (HS) and soft segment (SS) blocks produces a two-phase structure, which accounts for the elastomeric properties of these polymer systems. Polyurethanes are prepared with different HS and SS components, and HS:SS ratios, for various applications. Knowledge of the 3D morphology is necessary to understand polyurethane structure-property relationships. Although conventional transmission electron microscopy can image some polyurethanes, high voltage electron microscopy (HVEM) causes less radiation damage and images thicker samples at higher resolution, thus a sample region may be imaged at multiple tilt angles to provide 3D information. High resolution scanning electron microscopy (HR-SEM) provides complementary information, and at low accelerating voltages (1-3 keV), images near surface structures.Polyurethanes were examined with hard segments of methylene diphenylene diisocyanate (MDI) and 2000 MW soft segments of polytetramethylene oxide (PTMO), polybutadiene (PBD) and polydimethysiloxane (PDMS).

Preparation and properties of waterborne siloxane-containing polyurethane for moisture permeable textile coating

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Haibo Lei ◽  
Yunjun Luo ◽  
Zhen Ge ◽  
Xiaomeng Li ◽  
Shengpeng Wang
Keyword(s):  
Hard Segment ◽  
Soft Segment ◽  
Water Vapor Permeability ◽  
Mechanical Analysis ◽  
Vapor Permeability ◽  
Gravimetric Analysis ◽  
Scanning Calorimetry ◽  
Coated Fabric ◽  
Soft Segments ◽  
Textile Coating

AbstractWaterborne siloxane-containing polyurethanes (WSPU) were prepared by polyaddition reaction using poly(tetramethylene oxide)glycol (PTMG), polyethylene glycol (PEG), and α,ω-aminopropyl polydimethylsiloxane (APDMS) as mixing soft segments; 2,2-di(hydroxymethyl)propionic acid, as a hydrophilic chain extender; 1,4-butanediol and isophorone diisocyanate as hard segment; triethylamine as a neutralization agent. The thermal properties of WSPU films were analyzed by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermal gravimetric analysis (TGA). The mechanical properties of WSPU film were also investigated. Water vapor permeability (WVP) was examined according to GB_T 12704-1991. The DSC and DMA results indicated that there is a micro-phase separation in the WSPU film. The incorporation of APDMS into PU made the thermal stability of hard segment worse while that of soft segment better. The elasticity of WSPU was improved when the APDMS content was not more than 10%, the vapor permeability of coated fabric increased firstly and then decreased as the APDMS content increased, which was resulted from the hydrophilicity change and microstructure change of membrane. When 10% APDMS was incorporated into the WSPU, the WVP of coated fabric was 2130.15 g/(m2·24h), equal to one coated with a widely used solvent-based PU sample (UECCOAT), and the water resistance (WR) reached 30.0 KPa.

Smart Polymers and their Applications: A Review

2017 ◽  
Vol 8 (03) ◽  
Author(s):  
Gore S. A. ◽  
Gholve S. B. ◽  
Savalsure S. M. ◽  
Ghodake K. B. ◽  
Bhusnure O. G. ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Water Soluble ◽  
Solution Temperature ◽  
Smart Polymers ◽  
Stimuli Responsive ◽  
Responsive Materials ◽  
Water Soluble Polymers ◽  
Commercial Applications ◽  
Stimuli Sensitive ◽  
External Stimuli

Smart polymers are materials that respond to small external stimuli. These are also referred as stimuli responsive materials or intelligent materials. Smart polymers that can exhibit stimuli-sensitive properties are becoming important in many commercial applications. These polymers can change shape, strength and pore size based on external factors such as temperature, pH and stress. The stimuli include salt, UV irradiation, temperature, pH, magnetic or electric field, ionic factors etc. Smart polymers are very promising applicants in drug delivery, tissue engineering, cell culture, gene carriers, textile engineering, oil recovery, radioactive wastage and protein purification. The study is focused on the entire features of smart polymers and their most recent and relevant applications. Water soluble polymers with tunable lower critical solution temperature (LCST) are of increasing interest for biological applications such as cell patterning, smart drug release, DNA sequencing etc.

Sensitive Mechanocontrolled Luminescence in Cross-Linked Polymer Films

2019 ◽  
Author(s):  
Ayumu Karimata ◽  
Pradnya Patil ◽  
Eugene Khaskin ◽  
Sébastien Lapointe ◽  
robert fayzullin ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
Polymer Films ◽  
Soft Matter ◽  
Small Strain ◽  
Visual Methods ◽  
Photoluminescence Intensity ◽  
Stimuli Responsive ◽  
Responsive Materials ◽  
Highly Sensitive ◽  
Mechanical Stretching

Direct translation of mechanical force into changes in chemical behavior on a molecular level has important implication not only for the fundamental understanding of mechanochemical processes, but also for the development of new stimuli-responsive materials. In particular, detection of mechanical stress in polymers via non-destructive methods is important in order to prevent material failure and to study the mechanical properties of soft matter. Herein, we report that highly sensitive changes in photoluminescence intensity can be observed in response to the mechanical stretching of cross-linked polymer films when using stable, (pyridinophane)Cu-based dynamic mechanophores. Upon stretching, the luminescence intensity increases in a fast and reversible manner even at small strain (< 50%) and applied stress (< 0.1 MPa) values. Such sensitivity is unprecedented when compared to previously reported systems based on organic mechanophores. The system also allows for the detection of weak mechanical stress by spectroscopic measurements or by direct visual methods.<br>

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