A Novel Scheme for Prediction of Deformation Mechanisms of Block Copolymers Based on Phase Behavior

Weidisch, Roland; Ensslen, M.; Michler, Goerg H.; Arnold, M.; Budde, H.; Höring, S.; Fischer, H.

doi:10.1021/ma001272p

Cited by 19 publications

(29 citation statements)

References 29 publications

(87 reference statements)

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“…Block copolymers contain two or more chains connected by covalent bonds that offer a means of combining the desirable characteristics of different polymers into a hybrid material 22 . The mechanical properties and swellability of the outer region of the MNs can be controlled by manipulating the overall average molecular weight of the polymer and the weight fraction of each block 20, 23 . In this study, we chose a polystyrene- block -poly(acrylic acid) (PS- b -PAA) block copolymer as the swellable material and PS homopolymer as a non-swellable material.…”

Section: Resultsmentioning

confidence: 99%

A bio-inspired swellable microneedle adhesive for mechanical interlocking with tissue

et al. 2013

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Achieving significant adhesion to soft tissues while minimizing tissue damage poses a considerable clinical challenge. Chemical-based adhesives require tissue-specific reactive chemistry, typically inducing a significant inflammatory response. Staples are fraught with limitations including high-localized tissue stress and increased risk of infection, and nerve and blood vessel damage. Here, inspired by the endoparasite Pomphorhynchus laevis which swells its proboscis to attach to its host’s intestinal wall, we have developed a biphasic microneedle array that mechanically interlocks with tissue through swellable microneedle tips, achieving ~ 3.5 fold increase in adhesion strength compared to staples in skin graft fixation, and removal force of ~ 4.5 N/cm2 from intestinal mucosal tissue. Comprising a poly(styrene)-block-poly(acrylic acid) swellable tip and non-swellable polystyrene core, conical microneedles penetrate tissue with minimal insertion force and depth, yet high adhesion strength in their swollen state. Uniquely, this design provides universal soft tissue adhesion with minimal damage, less traumatic removal, reduced risk of infection and delivery of bioactive therapeutics.

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Section: Resultsmentioning

confidence: 99%

A bio-inspired swellable microneedle adhesive for mechanical interlocking with tissue

et al. 2013

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“…Previous studies in our laboratory have demonstrated HVEM as a valuable tool for studying the micromechanical processes of deformation in heterogeneous polymers including block copolymers. [28][29][30][31] With the help of the HVEM we have investigated the deformation structures in cylindrical (LN1) and lamellar (ST2) samples. Representative HVEM micrographs are given in Figure 8.…”

Section: Micromechanical Deformation Behaviourmentioning

confidence: 99%

“…[28][29][30][31] This method even allows an in situ observation of deformation mechanisms in polymeric materials. Compared with the ultra-thin sections about 50-100 nm thick used for TEM investigations, deformation structures observed in semi-thin sections used in HVEM investigations (thickness in the order of ca.…”

Section: Introductionmentioning

confidence: 99%

Correlation between Molecular Architecture, Morphology, and Deformation Behaviour of Styrene/Butadiene Block Copolymers

Adhikari

Michler

Huy

et al. 2003

Macro Chemistry & Physics

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The correlation between the molecular architecture, morphology, and micromechanical deformation behaviour of styrene/butadiene (SB) block copolymers with different architectures (linear and star block copolymers, total styrene content, ΦST = 0.74) was studied using dynamic mechanical analysis (DMA), uniaxial tensile testing, scanning force microscopy (SFM), and high voltage electron microscopy (HVEM). Deformation of the individual phases under uniaxial strain at the molecular level was monitored by Fourier transform infrared (FT‐IR) spectroscopy. It was demonstrated that the morphology and deformation behaviour of these block copolymers are strongly influenced by their molecular topology, block symmetry, and the nature of the interface between the component blocks. While the cylindrical morphology (hexagonal polybutadiene (PB) cylinders in polystyrene (PS) matrix) was observed in a symmetric SBS triblock copolymer with ΦST = 0.74, a “two‐component three‐phase” morphology was found in an asymmetric star block copolymer having an equivalent chemical composition and an SBS arm structure. Likewise, an SBS triblock copolymer with a composition identical to the former ones but with highly asymmetric PS end blocks revealed a lamellar morphology. While no locally confined deformation zones were observed in the lamellar block copolymers, the cylindrical block copolymer was found to deform through the formation of highly localised craze‐like deformation zones.

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“…9,10 They found that disordered block copolymers ( N < 10.5) with a PS-rich composition had a similar deformation mechanism to that of polystyrene, whereas microphase-separated block copolymers showed improved tensile properties. The greatest improvement in terms of high strength and toughness was observed for intermediately segregated block copolymers (12.5 < N < 95).…”

Section: Introductionmentioning

confidence: 99%

Effect of Thermal History and Microdomain Orientation on Deformation and Fracture Properties of Poly(cyclohexylethylene)−Polyethylene Triblock Copolymers Containing Cylindrical PE Domains

et al. 2002

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We investigate the effects of polyethylene cylinder domain orientation and thermal history on the micromechanical deformation and fracture properties of poly(cyclohexylethylene)-poly(ethylene)-poly(cyclohexylethylene) (CEC) triblock copolymer where the poly(cyclohexylethylene) (PCHE) blocks are unentangled. The properties are assessed using a "fragility" test in which copolymer films are strained in tension using a copper grid as a support. Optical microscopy was used to determine the statistics of deformation and fracture events while transmission electron microscopy (TEM) and scanning force microscopy (SFM) were used to investigate the morphological details of the plastically deformed regions. Films of CEC show much more ductility if the PE cylinders are oriented either randomly (spun-cast films) or parallel to the tensile direction than if the PE cylinders are perpendicular to the tensile direction. In the latter case craze breakdown and crack propagation can proceed within the unentangled PCHE matrix domain without the highly entangled PE cylinders bridging such cracks. For the highest molecular weight CEC physical aging of the PCHE glassy domains is also important in causing embrittlement. Removing such physical aging by quenching from above the glass transition temperature T g of PCHE causes a change in deformation mechanism from crazing in slowly cooled samples to a mixed case where crazing and shear deformation compete. Although the crystal morphology in the PE cylinders may also depend on the cooling rate during crystallization, it can be ruled out as the cause of the embrittlement since films physically aged below T g of PCHE but above the melting temperature of PE show brittle behavior when quenched from the aging temperature.

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A Novel Scheme for Prediction of Deformation Mechanisms of Block Copolymers Based on Phase Behavior

Cited by 19 publications

References 29 publications

A bio-inspired swellable microneedle adhesive for mechanical interlocking with tissue

A bio-inspired swellable microneedle adhesive for mechanical interlocking with tissue

Correlation between Molecular Architecture, Morphology, and Deformation Behaviour of Styrene/Butadiene Block Copolymers

Effect of Thermal History and Microdomain Orientation on Deformation and Fracture Properties of Poly(cyclohexylethylene)−Polyethylene Triblock Copolymers Containing Cylindrical PE Domains

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