Here we introduce a multifunctional copolymer network system with adjustable thermomechanical properties, which is also capable to show a substantial water uptake and in this way should allow the additional alteration of the overall elastic properties besides the variation of the crosslinking density. The swelling capacity in water, the thermal properties as well as the crystallinity of a series of grafted copolymer networks named CLEG composed of water swellable poly(ethylene glycol) (PEG) side chains and crystallizable poly(ε-caprolactone) (PCL) segments acting as covalent crosslinker were explored in an aqueous environment.

The water swelling capability of the CLEG polymer networks was found to increase from 120% to 240% with increasing weight content of PEG. In contrast to the dry state, where two well separated melting temperatures could be observed for all CLEG samples, in aqueous environment only one melting temperature slightly above 40 °C, was obtained, whereby the overall crystallinity after swelling with water was strongly related to the PCL content in the CLEG polymer networks.

A high modulus, sulfonated polymer synthesized from one-to-one ratio 4,6-bis(4-hydroxyphenyl)-N, N-diphenyl-1,3,5-triazin-2-amine and 4,4′-biphenol with bis(4-fluorophenyl) sulfone (DPA-PS:BP) is exploited as an ionomer for micro-ionic actuators. A unique and attractive feature of the ionomer is that it can contain high amounts of ionic liquid (IL) as an electrolyte while maintaining a high elastic modulus (i.e 600 MPa for 150 wt% uptake), which is more than one order of magnitude higher than the state-of-the-art of ionomers with working electrolytes. Such a high modulus makes it possible for the ionomer to be fabricated into micro-actuators with high uptake of ILs and low operation voltage (< 4 V), in various free standing forms with ion milling techniques, which are attractive for MEMS applications. As an initial demonstration of a DPA-PS:BP based ionic micro-actuator, a cantilever (200 μm x 33 μm x 5 μm) is manufactured by Focused Ion Beam (FIB) and characterized. Under the voltage of 1.6 V, the bending actuator exhibits an intrinsic strain from the active ionomer of 1.1% and a corresponding blocking force of 27 μN.

The shape-memory properties of electrospun polyetherurethanes (PEU) non-wovens with a single fiber diameter of around 1 μm were explored. In uniaxial cyclic, thermomechanical tensile tests a dual-shape shape-memory creation procedure (SMCP) was applied and the shape recovery was examined under stress-free and constant strain conditions. The thermal properties of the electrospun PEU non-wovens were found to be similar to those obtained for bulk PEU samples, whereas the mechanical properties revealed differences with respect to the elongation at break (εb) at increased temperatures. Excellent dual-shape properties were achieved for the PEU non-wovens with a high shape fixity rate (Rf) and shape recovery rate (Rr). A significant higher recovery stress (σmax) was obtained under constant strain recovery conditions for the electrospun non-wovens compared to the bulk PEU samples, which might be attributed to the higher degree of orientation of the polymer chains in the microfibers. Therefore the influence of different (single) fiber diameters as well as the variation of the programming elongation εm and temperature Tprog on σmax is an interesting issue for future investigations.

A triple-shape material based on the two crystallizable segments poly(ω‑pentadeca-lactone) and poly(ε-caprolactone) was synthesized by crosslinking star-shaped precursors. A newly developed programming procedure (TSCP2) was applied in order to achieve triple-shape behavior. The application of this modified triple-shape creation procedure enabled triple-shape capability by influencing the crystallization behavior of the two switching segments in these copolymer networks, which partly show no two distinct and separated melting points. The influence of molecular weight and content of the poly(ε-caprolactone) segment on the triple-shape effect programmed by application of TSCP2 was investigated.

Modern concepts for biofunctional implants often comprise the controlled release of bioactive compounds to gain specific biofunctionalities. Here, amorphous and semi-crystalline copolyester-based shape-memory polymer (SMP) networks are reported as matrix for pharmaceutical applications. Drug loading of such crosslinked networks by swelling techniques requires tools to determine the actual payload. In this report, the capability of determining loading kinetics by mass increase or changes of drug concentration in the swelling medium is explored for two types of copolyester-based SMP networks differing in their crosslinking chemistry. Nitrofurantoin and ethacridine lactate served as hydrophobic and hydrophilic model drugs. It was found, that the absolute values of the determined payload did not systematically agree with those obtained by the more reliable technique of network cleavage and spectrophotometric quantification. However, the studies indicate that for both types of SMP materials and both drugs, maximum incorporation of the drugs occurred within a few hours. The time until equilibration depended on the network properties.

A zeroth order dendritic carbosilane structure, SiFA4H with four hexafluoroisopropanol (HFIP) functional groups attached via propyl ligand arms to a central silicon atom, has been developed as a model hydrogen-bond (HB) acid sorbent coating and candidate reference HB acid. The HB donor interaction, through the hydroxyl of the HFIP moiety, with a solute HB base can be monitored by observing the hydroxyl stretching frequency through measurements of SiFA4H FTIR spectra before and during vapor exposure. HFIP hydroxyl stretch shifts, upwards of 700 cm-1 have been observed depending on the HB base. For a range of HB bases, the resulting hydroxyl stretch shifts correlate directly with the solute HB basicity scale, “B”, developed by Abraham et al [1]. A variety of techniques exist to measure solute HB basicity, however, the applicability to examine HB bases delivered as vapors or gases and the simplicity of the measurements described herein, with a reusable reference HB acid sorbent coating and standard FTIR spectrophotometer techniques is attractive for some applications including those with hazardous chemicals. Moreover, as an extension of this work we propose employing SiFA4H or related sorbents as molecular sensing coatings, where the semi-selective sorbent is examined by various infrared (IR) spectroscopic techniques to monitor and identify hazardous chemicals, taking advantage of molecular binding phenomena which occur in the sorbent [2].

Gelatin was functionalized with glycidyl methacrylate and photocrosslinked in the presence of poly(ethylene glycol) dimethacrylate (PEGDMA) or poly(ethylene glycol) monomethacrylate (PEGMA) to create a biopolymer-based system with tailorable properties. These co-networks were hydrolyzed using 6 M HCl and the degradation products were analyzed and identified using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry. This technique successfully identified gelatin-derived peptides such as FLPEPPE, SFLPEPPE, and SFLPEPPEE as well as an accompanying PEG-g-poly(methacrylic acid) component. No oligo- or polymethacrylates were monitored at any molecular weight range above m/z = 500, which indicated that they possessed lower molecular weights. An in vitro hydrolytic degradation experiment performed in pH 7.4 PBS buffer solution at 37 °C showed that these networks, which were prepared without the addition of a potentially toxic photoinitiator, exhibited mass loss of up to 50 wt% at 6 weeks of incubation time. These results provide valuable insight into how these functional gelatin-based co-network biomaterials will perform in a biological setting.

The paper deals with the synthesis and investigation of mechanical properties of multifunctional polyglycerol nanogels which consist of PEG with different chain lengths (glycerol, PEG 400, PEG 400-DGE, and PEG 1500). Their swelling behavior, elasticity, and stiffness are discussed in correlation with the PEG chain length. The nanogels built of PEG 400 exhibited most interesting and promising features and show the highest elasticity.

Today polysaccharide based hydrogel nanocomposites are receiving high importance as biomaterials for drug delivery. Inorganic nanoparticles (NPs) are incorporated into the polymer matrix to provide novel functionalities to the hydrogels. However, the effect of nanofillers on the release properties has not been totally understood. In this work, we investigate the influence of inorganic functional nanofillers (Fe3O4 and Au NPs) with variable size and shape on the structure of κ-carrageenan hydrogels and on the kinetics and release mechanism of methylene blue (MB) as model drug. It was shown that, depending on the nature of the nanofiller incorporated, and for equivalent nanofiller content, the mechanism of MB release can be adjusted either to by diffusion or polymer relaxation mechanism. The mechanism of the MB release was found to be determined by the strength and microstructure of the gel network and extent of gel swelling, which are affected by the extent of incorporation of the nanofillers.

An effective strategy to produce thermo-responsive islands-in-the-sea hydrogel nanofibres was developed using a single needle electrospinning setup. The produced hydrogel nanofibre mats not only showed excellent temperature response and high response speed, but also showed nanostructured surfaces.

The control of phase transition behavior in liquid crystalline polymers could enable potential application in the field of actuators and sensors by enabling a higher actuator performance of liquid crystalline elastomers (LCE). In this context the phase transition behavior of siloxane based liquid crystalline copolymers synthesized from 1,1,3,3-tetramethyldisiloxane, 2-methyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M-MeHq), and 2-tert-butyl-1,4-bis[4-(4-pentenyloxy)benzoyl]hydroquinone (M-tBHq) was explored. The selected monomers provided different thermal stabilities of the nematic phase, while the non-flexible siloxane spacer suppressed a smectic phase. The mesogenic properties were studied by means of differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and wide angle X-ray scattering (WAXS). With increasing fraction of M-MeHq the nematic phase of the copolymer was stabilized and a tailoring of relatively low TNI was achieved.

Reflective fibres were obtained in a two step process. First a core polyamide 6 fibre was spun from the melt and successively stretched. Then a chiral nematic liquid crystal coating was applied onto the surface of this fibre and further cured under UV light. The liquid crystal alignment was controlled by the molecular orientation of the polymer fibre and the 10 μm thick mono-domain coating presented a periodic helical organisation with a pitch of 350 nm. The obtained fibre showed strong Bragg reflection giving an intense green colour changing upon viewing angle. The fibre has been integrated into a fabric suggesting its application for textile design, fashion, and apparel.

Aerogels are quasi-stable, low-density, three-dimensional assemblies of nanoparticles, but they are commonly associated with poor mechanical properties. The most successful efforts to improve their mechanical properties involve cross-linking of the skeletal nanoparticles with polymers. However, post gelation cross-linking is time-consuming. Hence, it is reasonable to seek robust all-polymer aerogels among polymers known for their high mechanical strength. As a result, here we report the facile one-pot synthesis of a new class of Kevlar-like aerogels based on the rather underutilized reaction of multifunctional isocyanates and carboxylic acids. The resulting materials are up to 84% v/v porous with surface areas as high as 380 m2 g-1. The ultimate compressive strength per unit density is within 10% equal to that of Kevlar 49. The high specific energy absorption (37 J g-1) and Styrofoam-like thermal conductivity (0.028 W m-1 K-1) combined with thermal stability up to 350 °C render aramid aerogels multifunctional materials suitable for defense, civil and transportation related applications. Upon pyrolysis at 800 °C they can be converted to 80% (v/v) porous, electrically conducting carbons with surface areas as high as 474 m2 g-1.

High performance all-polymer aerogels are not only interesting for their low thermal conductivity, but also for their mechanical strength and their conversion to porous carbons. The prevalent design rule dictates that crosslinking at the monomer level decreases solubility of the developing polymer and induces phase separation of nanoparticles with high surface to volume ratios. Hence, hyperbranched structures based on trifunctional single aromatic core monomers should have enhanced interparticle connectivity and rigidity compared to those based on either difunctional or multiple aromatic core monomers. That design rule is applied here to hyperbranched polyurethane (PU) aerogels synthesized from tris(4-isocyanatophenyl)methane (TIPM) and 1,1,1-tris(4-hydroxyphenyl)ethane (HPE) in anhydrous acetone using dibutyltin dilaurate (DBTDL) as catalyst. The resulting materials vary from highly flexible to rigid as the monomer concentration increases. FTIR and 13C solid NMR confirm formation of urethane. SEM shows that the flexible variety is macroporous with a beaded worm-like structure, while the rigid variety is mesoporous and nanoparticulate. Lower-density flexible aerogels are highly porous (92%) with surface area of 132 m2 g-1, while the rigid ones have higher surface areas, up to 256 m2 g-1. Polyurethane aerogels from other triols and diols, e.g., phloroglucinol (POL) and resorcinol (RES), respectively, have also been studied and for similar monomer concentrations shrinkage and bulk density increases.

Asymmetry is intrinsic to natural systems and is widely used by living organisms for efficient adaptation, mimicry and movement. Polymer bilayers are the example of synthetic asymmetric systems, which are able to generate macroscopic motion and fold by forming different 3D objects such as tubes and capsules. Similar to bimetal films, the polymer bilayer consist of two substances with different swelling properties. One polymer is non-swellable and hydrophobic. Another polymer is water-swellable hydrogel. The folding, which might occur in response to temperature or pH, is caused by swelling of the hydrogel layer. The formed tubes and capsules can be manipulated using magnetic field. Reversible folding and unfolding of the polymer films is applied for reversible capture and release of cells in response to change of temperature and other signals. This novel biomimetic approach can be used for controlled encapsulation and release of microparticles, cells and drugs as well as fabrication of 3D scaffolds for tissue engineering.

Porous Si/hydrogel thin films combine a porous Si optical nanostructure and a functional hydrogel. These hybrids show great promise as versatile platforms for the fabrication of miniaturized sensors with various transduction mechanisms, cell culture supports, autonomous drug delivery systems, and many other functional systems. The basic considerations in designing functional PSi/hydrogel hybrids, synthesis routes, and novel characterization methods are discussed. New exciting applications of these nanomaterials as label-free optical biosensing platforms for bacteria and organophosphates detection are described.

Preparing porous biodegradable structures from shape memory polymers can combine the structure-defining properties of porous structures with the minimally invasive implanting possibilities of shape memory polymers. In this study, porous biodegradable shape memory structures were prepared using photo-crosslinked networks based on poly(D,L-lactide-co-trimethylene carbonate). The characteristic shape memory properties of the structures, such as their shape fixity at a low temperature of 0 oC and their full shape recovery upon heating to physiological temperatures, were excellent. This makes these biodegradable and biocompatible structures very well-suited for use as self-deploying implants in medical applications like tissue engineering, drug delivery and the support of soft tissues.

The generation of terminal N-Hydroxyl substituents in p-phenylene ethynylene based compounds is presented. P-phenylene ethynylene derivatives were synthesized in a Sonogashira coupling reaction. N-Hydroxyl groups could be introduced by lithiation of iodine moieties and subsequent reaction with the 2-methyl-2-nitrosopropane generated by the cleavage of its dimer. The synthesis by lithiation was found to be more effective compared to the reaction with the Grignard reagent and the chloro-derivative. The resulting compounds were characterized by 1H NMR, UV and PL spectroscopy and were shown to be sensitive towards oxidation. This new approach of introducing additional charge carriers by nitroxyl endgroups might enable conjugated polymers with enhanced conductivity.