Development of Thermally-Activated Shape Memory Polymers and Nanocomposites for Biomedical Devices

2017 ◽  
Author(s):  
Jingyu Wang ◽  
Shoieb Chowdhury ◽  
Yingtao Liu ◽  
Bradley Bohnstedt ◽  
Chung-Hao Lee
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Thermal Activation ◽  
Memory Function ◽  
Shape Memory Polymers ◽  
Thermally Activated

Shape memory polymers (SMPs) have been developed as an emerging technology platform for biomedical applications in the past decades. In particular, SMPs are clinically essential for the development of novel medical devices to significantly improve long-term surgical outcomes. In this paper, we synthesized and characterized thermally-activated aliphatic urethane SMPs fabricated with nanocomposites for the design and development of biomedical devices. The thermal activation of shape memory function was investigated by direct thermal activation. Critical polymer properties, such as the glass transition temperature and shape memory function, have been tailored to desired applications, by adjusting the polymer composition. Carbon nanotubes were uniformly dispersed within the polymer during nanocomposite fabrication to significantly enhance the thermal and electrical properties. The synthesized SMPs and nanocomposites were characterized to understand their thermal and mechanical properties using dynamic mechanical analysis (DMA). Scanning electron microscopy was employed to evaluate the dispersion of carbon nanotubes in polymer matrix. The mechanical properties of SMPs and nanocomposites at temperature above their glass transition temperature were evaluated using dog-bone samples in a dual-column mechanical testing system and an environmental chamber. SMPs and nanocomposites will then be fabricated in the form of foam for the development of novel devices applicable to endovascular embolization of cerebral aneurysms.

Free, partial, and fully constrained recovery analysis of cold-programmed shape memory epoxy/carbon nanotube nanocomposites: Experiments and predictions

2018 ◽  
Vol 29 (10) ◽  
pp. 2164-2176 ◽  
Author(s):  
R Abishera ◽  
R Velmurugan ◽  
KV Nagendra Gopal
Keyword(s):  
Glass Transition ◽  
Carbon Nanotube ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Thermally Activated ◽  
Large Structures ◽  
Multi Walled Carbon Nanotube ◽  
Optical Strain Measurement ◽  
Optical Strain

Thermally activated shape memory polymers are typically programmed by initially heating the material above the glass transition temperature ( Tg), deforming to the desired shape, cooling below Tg, and unloading to fix the temporary shape. This process of deforming at high temperatures becomes a time-, labor-, and energy-expensive process while applying to large structures. Alternatively, materials with reversible plasticity shape memory property can be programmed at temperatures well below the glass transition temperature which offers several advantages over conventional programming. Here, the free, partial, and fully constrained recovery analysis of cold-programmed multi-walled carbon nanotube–reinforced epoxy nanocomposites is presented. The free recovery analysis involves heating the temporary shape above Tg without any constraints (zero stress), and for fully constrained recovery analysis, the temporary shape is held constant while heating. The partially constrained recovery behavior is studied by applying a constant stress of 10%, 25%, and 50% of the maximum recovery stress obtained from the completely constrained recovery analysis. The samples are also characterized for their thermal, morphological, and mechanical properties. A non-contact optical strain measurement method is used to measure the strains during cold-programming and shape recovery. The different recovery behaviors are analyzed by using a thermo-viscoelastic–viscoplastic model, and the predictions are compared with the experimental results.

Optically transparent high temperature shape memory polymers

Soft Matter ◽  
2016 ◽  
Vol 12 (11) ◽  
pp. 2894-2900 ◽  
Author(s):  
Xinli Xiao ◽  
Xueying Qiu ◽  
Deyan Kong ◽  
Wenbo Zhang ◽  
Yanju Liu ◽  
...  
Keyword(s):  
Glass Transition ◽  
High Temperature ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Shape Memory ◽  
Shape Memory Polymers ◽  
Optically Transparent

Optically transparent shape memory polyimide exhibiting a glass transition temperature higher than those of other transparent shape memory polymers is reported.

scholarly journals Electrical Properties of Thiol-ene-based Shape Memory Polymers Intended for Flexible Electronics

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 902 ◽  
Author(s):  
Christopher L. Frewin ◽  
Melanie Ecker ◽  
Alexandra Joshi-Imre ◽  
Jonathan Kamgue ◽  
Jeanneane Waddell ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Electrical Properties ◽  
Shape Memory ◽  
Flexible Electronics ◽  
Shape Memory Polymers ◽  
Curing Process ◽  
Uv Curable ◽  
Processing Technologies

Thiol-ene/acrylate-based shape memory polymers (SMPs) with tunable mechanical and thermomechanical properties are promising substrate materials for flexible electronics applications. These UV-curable polymer compositions can easily be polymerized onto pre-fabricated electronic components and can be molded into desired geometries to provide a shape-changing behavior or a tunable softness. Alternatively, SMPs may be prepared as a flat substrate, and electronic circuitry may be built directly on top by thin film processing technologies. Whichever way the final structure is produced, the operation of electronic circuits will be influenced by the electrical and mechanical properties of the underlying (and sometimes also encapsulating) SMP substrate. Here, we present electronic properties, such as permittivity and resistivity of a typical SMP composition that has a low glass transition temperature (between 40 and 60 °C dependent on the curing process) in different thermomechanical states of polymer. We fabricated parallel plate capacitors from a previously reported SMP composition (fully softening (FS)-SMP) using two different curing processes, and then we determined the electrical properties of relative permittivity and resistivity below and above the glass transition temperature. Our data shows that the curing process influenced the electrical permittivity, but not the electrical resistivity. Corona-Kelvin metrology evaluated the quality of the surface of FS-SMP spun on the wafer. Overall, FS-SMP demonstrates resistivity appropriate for use as an insulating material.

Synergistic Physical Properties of Multiphase Nanocomposites with Carbon Nanotubes and Inorganic Particles

2007 ◽  
Vol 1056 ◽  
Author(s):  
Jan Sumfleth ◽  
Montira Sriyai ◽  
Luis Prado ◽  
Malte H.G. Wichmann ◽  
Karl Schulte
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Synergistic Effects ◽  
Inorganic Nanoparticles ◽  
Rheological Parameters ◽  
Inorganic Particles ◽  
Different Types

ABSTRACTMultiphase epoxy-nanocomposites based on multi-wall carbon nanotubes (MWCNT) and inorganic nanoparticles (TiO2) were produced. The rheological, electrical and thermo-mechanical properties were investigated in order to reveal informations about the interparticle interactions between the different types of nanoparticles. TEM-investigations reveal altered microstructures for the multiphase nanocomposites (MWCNT plus TiO2). TiO2 causes changes in the state of dispersion of MWCNT which can lead to an increase of the rheological parameters (e.g. G'). Due to changes in the formation of the percolated MWCNT network during curing, the electrical conductivity is decreased if the concentration of the non-conductive fillers exceeds a critical value. Additional synergistic effects could be found for the glass transition temperature. The presence of nanoparticles leads to a chemical inactivation of reactive groups of the matrix. Thus, the generated interphase between matrix and nanoparticles exhibits a lower curing degree which results in lower thermo-mechanical properties. For the multiphase systems the glass transition temperature is decreased less, due to an inactivation of the surface of the different types of nanoparticles by a self assembly which leads to a higher curing degree of the interphase.

Design and Analysis of a Self-Folding SMA-SMP Composite Laminate

2014 ◽  
Author(s):  
Robert Saunders ◽  
Darren Hartl ◽  
Richard Malak ◽  
Dimitris Lagoudas
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Shape Memory ◽  
Material Properties ◽  
Composite Laminate ◽  
Shape Memory Polymers ◽  
Thermally Activated ◽  
Planar Configuration ◽  
Shape Memory Composite ◽  
Reconfigurable Structure

Shape memory alloy (SMA) wires have the ability to create large actuation forces and displacements. When arranged in a planar configuration (e.g., in a mesh) and embedded near the surface of a polymer matrix, they can be used to create flat sheets that are self-folding and reconfigurable. Shape memory polymers (SMP) exhibit changes in material properties that allow them soften when heated above their glass transition temperature and then freeze when cooled back below it, retaining any deformation applied when they were softened. This work considers the design and analysis of key engineering features of a shape memory composite (SMC) laminate consisting of thermally activated SMA wires in a mesh pattern embedded in such an SMP matrix. Such a laminate would represent a relatively stiff reconfigurable structure with no need for continued power to retain actuated shapes. The results of the design study described herein will be an optimized configuration that maximizes the deflection of the laminate in its locked state while respecting conventional constraints against overstressing and overheating the SMA and SMP materials.

scholarly journals Studies on the Modification of Commercial Bisphenol-A-Based Epoxy Resin Using Different Multifunctional Epoxy Systems

2021 ◽  
Vol 2 (2) ◽  
pp. 419-430
Author(s):  
Ankur Bajpai ◽  
James R. Davidson ◽  
Colin Robert
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Bisphenol A ◽  
Epoxy Resin ◽  
Tensile Fracture ◽  
Chemical Structures ◽  
Amino Phenol ◽  
Epoxy Systems

The tensile fracture mechanics and thermo-mechanical properties of mixtures composed of two kinds of epoxy resins of different chemical structures and functional groups were studied. The base resin was a bi-functional epoxy resin based on diglycidyl ether of bisphenol-A (DGEBA) and the other resins were (a) distilled triglycidylether of meta-amino phenol (b) 1, 6–naphthalene di epoxy and (c) fluorene di epoxy. This research shows that a small number of multifunctional epoxy systems, both di- and tri-functional, can significantly increase tensile strength (14%) over neat DGEBA while having no negative impact on other mechanical properties including glass transition temperature and elastic modulus. In fact, when compared to unmodified DGEBA, the tri-functional epoxy shows a slight increase (5%) in glass transition temperature at 10 wt.% concentration. The enhanced crosslinking of DGEBA (90 wt.%)/distilled triglycidylether of meta-amino phenol (10 wt.%) blends may be the possible reason for the improved glass transition. Finally, the influence of strain rate, temperature and moisture were investigated for both the neat DGEBA and the best performing modified system. The neat DGEBA was steadily outperformed by its modified counterpart in every condition.

scholarly journals Synthesis, Properties, and Biodegradability of Thermoplastic Elastomers Made from 2-Methyl-1,3-propanediol, Glutaric Acid and Lactide

Life ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 43
Author(s):  
Lamya Zahir ◽  
Takumitsu Kida ◽  
Ryo Tanaka ◽  
Yuushou Nakayama ◽  
Takeshi Shiono ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Glutaric Acid ◽  
Triblock Copolymers ◽  
Tensile Tests ◽  
Thermoplastic Elastomers ◽  
Proteinase K ◽  
Synthesis Properties

An innovative type of biodegradable thermoplastic elastomers with improved mechanical properties from very common and potentially renewable sources, poly(L-lactide)-b-poly(2-methyl-1,3-propylene glutarate)-b-poly(L-lactide) (PLA-b-PMPG-b-PLA)s, has been developed for the first time. PLA-b-PMPG-b-PLAs were synthesized by polycondensation of 2-methyl-1,3-propanediol and glutaric acid and successive ring-opening polymerization of L-lactide, where PMPG is an amorphous central block with low glass transition temperature and PLA is hard semicrystalline terminal blocks. The copolymers showed glass transition temperature at lower than −40 °C and melting temperature at 130–152 °C. The tensile tests of these copolymers were also performed to evaluate their mechanical properties. The degradation of the copolymers and PMPG by enzymes proteinase K and lipase PS were investigated. Microbial biodegradation in seawater was also performed at 27 °C. The triblock copolymers and PMPG homopolymer were found to show 9–15% biodegradation within 28 days, representing their relatively high biodegradability in seawater. The macromolecular structure of the triblock copolymers of PLA and PMPG can be controlled to tune their mechanical and biodegradation properties, demonstrating their potential use in various applications.

scholarly journals Buckling and vibration analysis of shape memory laminated composite beams under axially heterogeneous in-plane loads in the glass transition temperature region

2021 ◽  
Vol 3 (4) ◽  
Author(s):  
Nilesh Tiwari ◽  
A. A. Shaikh
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Boundary Conditions ◽  
Shape Memory ◽  
Transition Region ◽  
Shape Memory Polymer ◽  
Shear Deformation Theory ◽  
Effect Of Temperature ◽  
Glass Transition Region

AbstractBuckling and vibration study of the shape memory polymer composites (SMPC) across the glass transition temperature under heterogeneous loading conditions are presented. Finite element analysis based on C° continuity equation through the higher order shear deformation theory (HSDT) is employed considering non linear Von Karman approach to estimate critical buckling and vibration for the temperature span from 273 to 373 K. Extensive numerical investigations are presented to understand the effect of temperature, boundary conditions, aspect ratio, fiber orientations, laminate stacking and modes of phenomenon on the buckling and vibration behavior of SMPC beam along with the validation and convergence study. Effect of thermal conditions, particularly in the glass transition region of the shape memory polymer, is considerable and presents cohesive relation between dynamic modulus properties with magnitude of critical buckling and vibration. Moreover, it has also been inferred that type of axial loading condition along with the corresponding boundary conditions significantly affect the buckling and vibration load across the glass transition region.

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