Multiphase thermoplastic elastomers by combination of covalent and association chain structures: 2. Small-strain dynamic mechanical properties

Hilger, Christopher; Stadler, Reimund; Liane, L.; Freitas, de Lucca

doi:10.1016/0032-3861(90)90040-6

Cited by 50 publications

(29 citation statements)

References 16 publications

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“…Figure B illustrates reversible association of multiple H‐bonding between thymine/diamino triazine (THY/DAT), thymine/2,6‐diamino‐pyridine (THY/DAP), and barbiturate/Hamilton wedge (Ba/HW), which have similar structural units. Polymers end functionalized with such associative groups are capable of assembling into strong rubber‐like material . Enhanced mechanical strength is not simply due to the presence of multiple H‐bonds, but also cluster formations from the H‐bonding moieties which result in phase segregation.…”

Section: H‐bondingmentioning

confidence: 99%

“…Self‐repairing is shown in PIB networks containing Ba/HW associative pairs. [12d] These materials showed a rubbery plateau at high shear rates, and self‐healing under ambient conditions by bringing two physically separated parts into contact. Notably, polarity difference between associative chain ends and aliphatic polymer backbones enhanced the cluster formation.…”

Section: H‐bondingmentioning

confidence: 99%

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Self‐Healing of Polymers via Supramolecular Chemistry

Yang

Urban

2018

Adv Materials Inter

155

117

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rearrangements. While one challenge is to incorporate chemical modifications enabling chemical bond reformations, equally important is the coordination of chemical events with polymer network physical changes within interfacial regions resulting from mechanical damage.Recent studies suggested that two types of dynamic bonds are highly attractive to achieve self-healing in polymers: reversible covalent bonds and supramolecular chemistry. Reversible covalent bonds offer higher bonding energies, allowing the material to regain physical properties similar to conventional polymers prior to damage. Advantages and disadvantages of reversible covalent bonding were summarized in several review articles. [5] Self-healing involving dynamic dissociation/association using supramolecular chemistry offers fast reversibility under ambient conditions reaching exceptionally quickly equilibrium state, bonding directionality, and remarkable sensitivity. Since broad-range of network structures can be obtained via supramolecular interactions, applications in soft electronics, sensing, biomedical technologies, 3-4D printing, and reprocessable materials are highly attractive and may open many new technological opportunities (Figure 1). Mechanical integrity using supramolecular chemistry is achieved by the formation of multiple noncovalent interactions between multiple associative groups covalently attached to polymer side chain or chain ends of macromolecular building blocks. These interactions include H-bonding, metal-ligand complexation, hostguest, ionic interactions, π-π stacking, and hydrophobic interactions. They are depicted in Figure 1. In contrast to covalent rebonding, mechanical properties of supramolecular polymer networks are achieved by the presence of these secondary interactions forming noncovalent crosslinks, which bind liquid-like building blocks into plastic or rubbery polymers in hydrated and nonhydrated states. The dynamic nature of these noncovalent bonds provides an opportunity for self-healing attributed to reassociation of supramolecular components, similar to secondary interactions found in living systems that regulate many living functions. The rule of thumb in designing these networks is that the degree of association is determined by the equilibrium constant (K a ) values, whereas dynamics is driven by rate constants of the association-dissociation reactions, k a and k d , respectively. [6] Molecular structural and electronic features along with network heterogeneities are of particular importance in these networks. Mechanical strength and elasticity of supramolecular polymers are determined by not only the K a values, but also stacking and clustering of the associative groups which may result in heterogeneities leading to the Recent advances of supramolecular chemistry utilized in the development of self-healing polymers have revealed that the rate and equilibrium constants of bond dissociation/re-association, bonding directionality, chain relaxation time, decay rate of chain relaxation after damage, and clu...

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Section: H‐bondingmentioning

confidence: 99%

Section: H‐bondingmentioning

confidence: 99%

Self‐Healing of Polymers via Supramolecular Chemistry

Yang

Urban

2018

Adv Materials Inter

155

117

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“…As network formation is a central feature of all these materials, the nature of the underlying hydrogen bond plays a central role, determining the final material properties. An early example of hydrogen‐bonded networks has been reported by the group of Stadler et al,4–9 where uradiazole moieties served as reversible crosslinks between poly(butadiene) chains generating thermoplastic materials from rubbers. Other examples that lead to a drastic change of polymer properties by the use of hydrogen‐bonding moieties mediating network formation include the use of specifically weak (diamino‐triazine/thymine,10–14 adenine/thymine,15 and cytosine/thymine15,16), strong (such as ureidopyrimidines,17–20 barbiturate/Hamilton receptor1,16,21–26), or cooperative hydrogen‐bonding moieties (such as the use of ureas in the formation of interlocked fibers,27–32 or thermoplastics33), which is especially useful in the design of self‐healing polymers 34,35.…”

Section: Introductionmentioning

confidence: 99%

Studies of chitosan. I. Preparation and characterization of chitosan/poly(vinyl alcohol) blend films

Chen

Wang

Mao

et al. 2007

J of Applied Polymer Sci

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Various blending ratios of chitosan/poly-(vinyl alcohol) (CS/PVA) blend films were prepared by solution blend method in this study. The thermal properties and chemical structure characterization of the CS/PVA blend films were examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and Fourier transform infrared (FTIR). Based upon the observation on the DSC thermal analysis, the melting point of PVA is decreased when the amount of CS in the blend film is increased. The FTIR absorption characteristic is changed when the amount of CS in the blend film is varied. Results of X-ray diffraction (XRD) analysis indicate that the intensity of diffraction peak at 198 of PVA becomes lower and broader with increasing the amount of CS in the CS/ PVA blend film. This trend illustrates that the existence of CS decreases the crystallinity of PVA. Although both PVA and CS are hydrophilic biodegradable polymers, the results of water contact angle measurement are still shown as high as 688 and 838 for PVA and for CS films, respectively. A minimum water contact angle (568) was observed when the blend film contains 50 wt % CS.

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“…As the concentration of secondary interactions per unit volume increases in a synthetic associating polymer, one will approach the critical concentration required for gelation, that is, the conversion of a viscoelastic liquid to a viscoelastic solid (Rubinstein and Semenov 1998). More extensive substitution along the backbone in bulk associating polymers can actually result in the formation of thermoplastic elastomers that display a well-developed rubbery plateau similar to a covalently cross-linked rubber, except that the material can be melted and recycled, unlike a cross-linked rubber (Hilger et al 1990). Those authors showed that development of such a rubber-like quality in thermoplastic elastomers resulted from phase-separation of extended hydrogen bonding domains, which were extensive enough to give rise to a differential scanning calorimetry (DSC) melting endotherm.…”

Section: Discussionmentioning

confidence: 99%

Effect of Moisture Content on Viscoelastic Properties of Hydrated Gliadin

2004

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Cereal Chem. 81(2):207-219The effect of moisture content on the linear viscoelastic properties of gliadin hydrated to 30 and 40% moisture content [gliadin(30%) and gliadin(40%), respectively] was determined. These two moisture contents bracketed the equilibrium moisture content of gliadin, which was 37.6%. Time-temperature-superposition was used to develop master curves of the elastic modulus (G′), viscous modulus (G′′), dynamic viscosity (η′), and tan δ (G′′/G′) from isothermal frequency sweep data obtained at 25-80°C.Smooth master curves were obtained for all of the viscoelastic functions for both gliadins. G′ and G′′ showed a power law dependency on frequency (with G′′ > G′) for frequencies <0.1 rad/sec for gliadin(30%) and <1 rad/sec for gliadin(40%). The low-frequency-limiting slopes on log-log coordinates for G′ and G′′ were 0.700 and 0.646 for gliadin(30%), respectively. Corresponding values were 0.658 and 0.614 for gliadin(40%). G′ crossed over G′′ at a frequency of ≈0.3 rad/sec for gliadin(30%), while G′ and G′′ for gliadin(40%) only became congruent at higher frequencies.Both gliadin samples showed appreciable frequency dependence of η′ over the entire frequency range, while η′ was greater for gliadin(30%) than for gliadin(40%) at all frequencies, but especially at the lowest frequencies. Tan δ increased gradually from a value of ≈1 at 0.1 rad/sec to ≈2 at the lowest frequency of 0.0002 rad/sec for both gliadins, but tan δ decreased rapidly for gliadin(30%) for frequencies >0.1 rad/sec. Thus, the main difference between gliadin(30%) and gliadin(40%) was that elastic effects (G′ > G′′ and decreased tan δ were more prominent for gliadin(30%) at the higher frequencies. In addition, the frequency dependence of G′, G′′, η′, and tan δ for the two gliadin samples was compared directly with two samples of poly(dimethylsiloxane) (PDMS) a linear silicone-based entangled polymer with molecular weights (MW) of 140,000 and 385,000. The substantial differences in the magnitude and overall patterns of the frequency dependence of the viscoelastic functions between the gliadin and PDMS samples was attributed to the dominant effect that noncovalent secondary associations apparently have on the linear viscoelasticity of the gliadins. The energy of activation for flow (determined from the temperature dependence of the shift factors) for the gliadin samples for the range 25-45°C was higher than is typical for entangled linear polymer melts. The activation energy decreased for temperatures greater than ≈60°C for gliadin(30%) and ≈50°C for gliadin(40%). Thus, hydrated gliadin cannot be considered to be a simple viscoelastic liquid.

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Multiphase thermoplastic elastomers by combination of covalent and association chain structures: 2. Small-strain dynamic mechanical properties

Cited by 50 publications

References 16 publications

Self‐Healing of Polymers via Supramolecular Chemistry

Self‐Healing of Polymers via Supramolecular Chemistry

Studies of chitosan. I. Preparation and characterization of chitosan/poly(vinyl alcohol) blend films

Effect of Moisture Content on Viscoelastic Properties of Hydrated Gliadin

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