TY - JOUR
A1 - Tentschert, Jutta
A1 - Jungnickel, Harald
A1 - Reichardt, Philipp
A1 - Leube, Peter
A1 - Kretzschmar, Bernd
A1 - Taubert, Andreas
A1 - Luch, A.
T1 - Identification of nano clay in composite polymers
JF - Surface and interface analysis : an international journal devoted to the development and application of techniques for the analysis surfaces, interfaces and thin films
N2 - Industrialized food production is in urgent search for alternative packaging materials, which can serve the requirements of a globalized world in terms of longer product shelf lives, reduced freight weight to decrease transport costs, and better barrier functionality to preserve its freshness. Polymer materials containing organically modified nano clay particles as additives are one example for a new generation of packaging materials with specific barrier functionality to actually hit the market. Clay types used for these applications are aluminosilicates, which belong to the mineral group of phyllosilicates. These consist of nano-scaled thin platelets, which are organically modified with quaternary ammonium compounds acting as spacers between the different clay layers, thereby increasing the hydrophobicity of the mineral additive. A variety of different organically modified clays are already available, and the use as additive for food packaging materials is one important application. To ensure valid risk assessments of emerging nano composite polymers used in the food packaging industry, exact analytical characterization of the organically modified clay within the polymer matrix is of paramount importance. Time-of-flight SIMS in combination with multivariate statistical analysis was used to differentiate modified clay reference materials from another. Time-of-flight SIMS spectra of a reference polymer plate, which contained one specific nano clay composite, were acquired. For each modified clay additive, a set of characteristic diagnostic ions could be identified, which then was used to successfully assign unknown clay additives to the corresponding reference material. Thus, the described methodology could be used to define and characterize nano clay within polymer matrices. Copyright (c) 2014 John Wiley & Sons, Ltd.
KW - ToF-SIMS
KW - nanoparticles
KW - nano clay
KW - polymer
KW - food contact material
Y1 - 2014
U6 - https://doi.org/10.1002/sia.5546
SN - 0142-2421
SN - 1096-9918
VL - 46
SP - 334
EP - 336
PB - Wiley-Blackwell
CY - Hoboken
ER -
TY - JOUR
A1 - Lützow, Karola
A1 - Weigel, Thomas
A1 - Lendlein, Andreas
T1 - Solvent-based fabrication method for magnetic, shape-memory nanocomposite foams
JF - MRS advances
N2 - This paper presents shape-memory foams that can be temporarily fixed in their compressed state and be expanded on demand. Highly porous, nanocomposite foams were prepared from a solution of polyetherurethane with suspended nanoparticles (mean aggregate size 90 nm) which have an iron(III) oxide core with a silica shell. The polymer solution with suspended nanoparticles was cooled down to -20 degrees C in a two-stage process, which was followed by freeze-drying. The average pore size increases with decreasing concentration of nanoparticles from 158 mu m to 230 mu m while the foam porosity remained constant. After fixation of a temporary form of the nanocomposite foams, shape recovery can be triggered either by heat or by exposure to an alternating magnetic field. Compressed foams showed a recovery rate of up to 76 +/- 4% in a thermochamber at 80 degrees C, and a slightly lower recovery rate of up to 65 +/- 4% in a magnetic field.
KW - composite
KW - foam
KW - polymer
KW - magnetic
KW - shape memory
Y1 - 2020
U6 - https://doi.org/10.1557/adv.2019.422
SN - 2059-8521
VL - 5
IS - 14-15
SP - 785
EP - 795
PB - Cambridge Univ. Press
CY - Cambridge
ER -
TY - JOUR
A1 - Behl, Marc
A1 - Zhao, Qian
A1 - Lendlein, Andreas
T1 - Glucose-responsive shape-memory cryogels
JF - Journal of materials research : JMR
N2 - Boronic ester bonds can be reversibly formed between phenylboronic acid (PBA) and triol moieties. Here, we aim at a glucose-induced shape-memory effect by implementing such bonds as temporary netpoints, which are cleavable by glucose and by minimizing the volume change upon stimulation by a porous cryogel structure. The polymer system consisted of a semi-interpenetrating network (semi-IPN) architecture, in which the triol moieties were part of the permanent network and the PBA moieties were located in the linear polymer diffused into the semi-IPN. In an alkaline medium (pH = 10), the swelling ratio was approximately 35, independent of C-glu varied between 0 and 300 mg/dL. In bending experiments, shape fixity R-f approximate to 80% and shape recovery R-r approximate to 100% from five programming/recovery cycles could be determined. R-r was a function of C-glu in the range from 0 to 300 mg/dL, which accords with the fluctuation range of C-glu in human blood. In this way, the shape-memory hydrogels could play a role in future diabetes treatment options.
KW - shape memory
KW - polymer
KW - porosity
Y1 - 2020
U6 - https://doi.org/10.1557/jmr.2020.204
SN - 0884-2914
SN - 2044-5326
VL - 35
IS - 18
SP - 2396
EP - 2404
PB - Springer
CY - Berlin
ER -
TY - JOUR
A1 - Balk, Maria
A1 - Behl, Marc
A1 - Lendlein, Andreas
T1 - Actuators based on oligo[(epsilon-caprolactone)-co-glycolide] with accelerated hydrolytic degradation
JF - MRS advances : a journal of the Materials Research Society (MRS)
N2 - Polyester-based shape-memory polymer actuators are multifunctional materials providing reversible macroscopic shape shifts as well as hydrolytic degradability. Here, the function-function interdependencies (between shape shifts and degradation behaviour) will determine actuation performance and its life time. In this work, glycolide units were incorporated in poly(epsilon-caprolactone) based actuator materials in order to achieve an accelerated hydrolytic degradation and to explore the function-function relationship. Three different oligo[(epsilon-caprolactone)-co-glycolide] copolymers (OCGs) with similar molecular weights (10.5 +/- 0.5 kg center dot mol(-1)) including a glycolide content of 8, 16, and 26 mol% (ratio 1:1:1 wt%) terminated with methacrylated moieties were crosslinked. The obtained actuators provided a broad melting transition in the range from 27 to 44 degrees C. The hydrolytic degradation of programmed OCG actuators (200% of elongation) resulted in a reduction of sample mass to 51 wt% within 21 days at pH = 7.4 and 40 degrees C. Degradation results in a decrease of T-m associated to the actuating units and increasing T-m associated to the skeleton forming units. The actuation capability decreased almost linear as function of time. After 11 days of hydrolytic degradation the shape-memory functionality was lost. Accordingly, a fast degradation behaviour as required, e.g., for actuator materials intended as implant material can be realized.
KW - actuation
KW - shape memory
KW - polymer
KW - crystalline
Y1 - 2020
U6 - https://doi.org/10.1557/adv.2019.447
SN - 2059-8521
VL - 5
IS - 12-13
SP - 655
EP - 666
PB - Cambridge University Press
CY - New York, NY
ER -
TY - JOUR
A1 - Izraylit, Victor
A1 - Gould, Oliver E. C.
A1 - Kratz, Karl
A1 - Lendlein, Andreas
T1 - Investigating the phase-morphology of PLLA-PCL multiblock copolymer/PDLA blends cross-linked using stereocomplexation
JF - MRS advances
N2 - The macroscale function of multicomponent polymeric materials is dependent on their phase-morphology. Here, we investigate the morphological structure of a multiblock copolymer consisting of poly(L-lactide) and poly(epsilon-caprolactone) segments (PLLA-PCL), physically cross-linked by stereocomplexation with a low molecular weight poly(D-lactide) oligomer (PDLA). The effects of blend composition and PLLA-PCL molecular structure on the morphology are elucidated by AFM, TEM and SAXS. We identify the formation of a lattice pattern, composed of PLA domains within a PCL matrix, with an average domain spacing d0 = 12 - 19 nm. The size of the PLA domains were found to be proportional to the block length of the PCL segment of the copolymer and inversely proportional to the PDLA content of the blend. Changing the PLLA-PCL / PDLA ratio caused a shift in the melt transition Tm attributed to the PLA stereocomplex crystallites, indicating partial amorphous phase dilution of the PLA and PCL components within the semicrystalline material. By elucidating the phase structure and thermal character of multifunctional PLLA-PCL / PDLA blends, we illustrate how composition affects the internal structure and thermal properties of multicomponent polymeric materials. This study should facilitate the more effective incorporation of a variety of polymeric structural units capable of stimuli responsive phase transitions, where an understanding the phase-morphology of each component will enable the production of multifunctional soft-actuators with enhanced performance.
KW - polymer
KW - blend
KW - nanostructure
KW - morphology
Y1 - 2020
U6 - https://doi.org/10.1557/adv.2019.465
SN - 2059-8521
VL - 5
IS - 14-15
SP - 699
EP - 707
PB - Cambridge Univ. Press
CY - New York
ER -
TY - JOUR
A1 - Behl, Marc
A1 - Balk, Maria
A1 - Mansfeld, Ulrich
A1 - Lendlein, Andreas
T1 - Phase morphology of multiblock copolymers differing in sequence of blocks
JF - Macromolecular materials and engineering
N2 - The chemical nature, the number length of integrated building blocks, as well as their sequence structure impact the phase morphology of multiblock copolymers (MBC) consisting of two non-miscible block types. It is hypothesized that a strictly alternating sequence should impact phase segregation. A library of well-defined MBC obtained by coupling oligo(epsilon-caprolactone) (OCL) of different molecular weights (2, 4, and 8 kDa) with oligotetrahydrofuran (OTHF, 2.9 kDa) via Steglich esterification results in strictly alternating (MBCalt) or random (MBCran) MBC. The three different series has a weight average molecular weight (M-w) of 65 000, 165 000, and 168 000 g mol(-1) for MBCalt and 80 500, 100 000, and 147 600 g mol(-1) for MBCran. When the chain length of OCL building blocks is increased, the tendency for phase segregation is facilitated, which is attributed to the decrease in chain mobility within the MBC. Furthermore, it is found that the phase segregation disturbs the crystallization by causing heterogeneities in the semi-crystalline alignment, which is attributed to an increase of the disorder of the OCL semi-crystalline alignment.
KW - electron microscopy
KW - multiblock copolymers
KW - phase morphology
KW - polymer
KW - libraries
KW - sequence structures
KW - wide angle x‐ ray scattering
Y1 - 2021
U6 - https://doi.org/10.1002/mame.202000672
SN - 1439-2054
VL - 306
IS - 3
PB - Wiley-VCH
CY - Weinheim
ER -
TY - JOUR
A1 - Braune, S.
A1 - Baeckemo, J.
A1 - Lau, S.
A1 - Heuchel, M.
A1 - Kratz, K.
A1 - Jung, F.
A1 - Reinthaler, M.
A1 - Lendlein, Andreas
T1 - The influence of different rewetting procedures on the thrombogenicity of nanoporous poly(ether imide) microparticles
JF - Clinical hemorheology and microcirculation : blood flow and vessels
N2 - Nanoporous microparticles prepared from poly(ether imide) (PEI) are discussed as candidate adsorber materials for the removal of uremic toxins during apheresis. Polymers exhibiting such porosity can induce the formation of micro-gas/air pockets when exposed to fluids. Such air presenting material surfaces are reported to induce platelet activation and thrombus formation. Physical or chemical treatments prior to implantation are discussed to reduce the formation of such gas nuclei. Here, we report about the influence of different rewetting procedures - as chemical treatments with solvents on the thrombogenicity of hydrophobic PEI microparticles and PEI microparticles hydrophilized by covalent attachment of poly(vinyl pyrrolidone) (PVP) of two different chain lengths.
Autoclaved dry PEI particles of all types with a diameter range of 200 - 250 mu m and a porosity of about 84%+/- 2% were either rewetted directly with phosphate buffered saline (24 h) or after immersion in an ethanol-series. Thrombogenicity of the particles was studied in vitro upon contact with human sodium citrated whole blood for 60 min at 5 rpm vertical rotation. Numbers of non-adherent platelets were quantified, and adhesion of blood cells was qualitatively analyzed by bright field microscopy. Platelet activation (percentage of CD62P positive platelets and amounts of soluble P-Selectin) and platelet function (PFA100 closure times) were analysed.
Retention of blood platelets on the particles was similar for all particle types and both rewetting procedures. Non-adherent platelets were less activated after contact with ethanol-treated particles of all types compared to those rewetted with phosphate buffered saline as assessed by a reduced number of CD62P-positive platelets and reduced amounts of secreted P-Selectin (P < 0.05 each). Interestingly, the hydrophilic surfaces significantly increased the number of activated platelets compared to hydrophobic PEI regardless of the rewetting agent. This suggests that, apart from wettability, other material properties might be more important to regulate platelet activation. PFA100 closure times were reduced and within the reference ranges in the ethanol group, however, significantly increased in the saline group. No substantial difference was detected between the tested surface modifications. In summary, rewetting with ethanol resulted in a reduced thrombogenicity of all studied microparticles regardless of their wettability, most likely resulting from the evacuation of air from the nanoporous particles.
KW - biomaterial
KW - polymer
KW - microparticle
KW - thrombogenicity
KW - hemocompatibility
KW - dynamic in-vitro test
KW - rewetting
Y1 - 2021
U6 - https://doi.org/10.3233/CH-201029
SN - 1386-0291
SN - 1875-8622
VL - 77
IS - 4
SP - 367
EP - 380
PB - IOS Press
CY - Amsterdam
ER -
TY - JOUR
A1 - Abbasi, Ali
A1 - Xu, Yaolin
A1 - Khezri, Ramin
A1 - Etesami, Mohammad
A1 - Lin, C.
A1 - Kheawhom, Soorathep
A1 - Lu, Yan
T1 - Advances in characteristics improvement of polymeric membranes/separators for zinc-air batteries
JF - Materials Today Sustainability
N2 - Zinc-air batteries (ZABs) are gaining popularity for a wide range of applications due to their high energy density, excellent safety, and environmental friendliness. A membrane/separator is a critical component of ZABs, with substantial implications for battery performance and stability, particularly in the case of a battery in solid state format, which has captured increased attention in recent years. In this review, recent advances as well as insight into the architecture of polymeric membrane/separators for ZABs including porous polymer separators (PPSs), gel polymer electrolytes (GPEs), solid polymer electrolytes (SPEs) and anion exchange membranes (AEMs) are discussed. The paper puts forward strategies to enhance stability, ionic conductivity, ionic selectivity, electrolyte storage capacity and mechanical properties for each type of polymeric membrane. In addition, the remaining major obstacles as well as the most potential avenues for future research are examined in detail.
KW - Ionic selectivity
KW - Ionic conductivity
KW - Gel polymer
KW - Ion exchange
KW - Porous
KW - polymer
Y1 - 2022
U6 - https://doi.org/10.1016/j.mtsust.2022.100126
SN - 2589-2347
VL - 18
PB - Elsevier
CY - Amsterdam
ER -