Influence of POSS Type on the Space Environment Durability of Epoxy-POSS Nanocomposites

In order to use polymers at low Earth orbit (LEO) environment, they must be protected against atomic oxygen (AO) erosion. A promising protection strategy is to incorporate polyhedral oligomeric silsesquioxane (POSS) molecules into the polymer backbone. In this study, the space durability of epoxy-POSS (EPOSS) nanocomposites was investigated. Two types of POSS molecules were incorporated separately—amine-based and epoxy-based. The outgassing properties of the EPOSS, in terms of total mass loss, collected volatile condensable material, and water vapor regain were measured as a function of POSS type and content. The AO durability was studied using a ground-based AO simulation system. Surface compositions of EPOSS were studied using high-resolution scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that with respect to the outgassing properties, only some of the EPOSS compositions were suitable for the ultrahigh vacuum space environment, and that the POSS type and content had a strong effect on their outgassing properties. Regardless of the POSS type being used, the AO durability improved significantly. This improvement is attributed to the formation of a self-passivated AO durable SiO2 layer, and demonstrates the potential use of EPOSS as a qualified nanocomposite for space applications.

Options to Improve the Mechanical Properties of Protein-Based Materials

While bio-based but chemically synthesized polymers such as polylactic acid require industrial conditions for biodegradation, protein-based materials are home compostable and show high potential for disposable products that are not collected. However, so far, such materials lack in their mechanical properties to reach the requirements for, e.g., packaging applications. Relevant measures for such a modification of protein-based materials are plasticization and cross-linking; the former increasing the elasticity and the latter the tensile strength of the polymer matrix. The assessment shows that compared to other polymers, the major bottleneck of proteins is their complex structure, which can, if developed accordingly, be used to design materials with desired functional properties. Chemicals can act as cross-linkers but require controlled reaction conditions. Physical methods such as heat curing and radiation show higher effectiveness but are not easy to control and can even damage the polymer backbone. Concerning plasticization, effectiveness and compatibility follow opposite trends due to weak interactions between the plasticizer and the protein. Internal plasticization by covalent bonding surpasses these limitations but requires further research specific for each protein. In addition, synergistic approaches, where different plasticization/cross-linking methods are combined, have shown high potential and emphasize the complexity in the design of the polymer matrix.

Random and Diblock Thermoresponsive Oligo(ethylene glycol)-Based Copolymers Synthesized via Photo-Induced RAFT Polymerization

Amphiphilic random and diblock thermoresponsive oligo(ethylene glycol)-based (co)polymers were synthesized via photoiniferter polymerization under visible light using trithiocarbonate as a chain transfer agent. The effect of solvent, light intensity and wavelength on the rate of the process was investigated. It was shown that blue and green LED light could initiate RAFT polymerization of macromonomers without an exogenous initiator at room temperature, giving bottlebrush polymers with low dispersity at sufficiently high conversions achieved in 1–2 h. The pseudo-living mechanism of polymerization and high chain-end fidelity were confirmed by successful chain extension. Thermoresponsive properties of the copolymers in aqueous solutions were studied via turbidimetry and laser light scattering. Random copolymers of methoxy- and alkoxy oligo(ethylene glycol) methacrylates of a specified length formed unimolecular micelles in water with a hydrophobic core consisting of a polymer backbone and alkyl groups and a hydrophilic oligo(ethylene glycol) shell. In contrast, the diblock copolymer formed huge multimolecular micelles.

Tandem Osmotic Engine Based on Hydrogel Particles with Antipolyelectrolyte and Polyelectrolyte Effect Fuelled by Both Salinity Gradient Modes

In this study, we propose a new approach to attain energy by salinity gradient engines with pistons based on hydrogels possessing polyelectrolyte and antipolyelectrolyte effects in a tandem arrangement, providing energy in each salinity gradient mode in a repeatable manner. The swelling of hydrogel with a polyelectrolyte effect and shrinking of hydrogel particles possessing an antipolyelectrolyte effect in desalinated water, and subsequent shrinking of hydrogel with polyelectrolyte and swelling of hydrogel antipolyelectrolyte effect in saline water, generate power in both increasing and decreasing salinity modes. To investigate the energy recovery, we scrutinized osmotic engine assemblies by a setup arrangement of pistons with hydrogel particles, with polyelectrolyte and antipolyelectrolyte effects, in tandem. The energy recovery from the tandem engine setup (calculated based on dry form for each polyelectrolyte polyacrylate-based hydrogel-SPA) and antipolyelectrolyte–sulfobetaine-based gel with methacrylate polymeric backbone-SBE) up to 581 J kg−1 and a mean power of 0.16 W kg−1 was obtained by the tandem setup of SPA and SBE hydrogel containing 3% crosslinking density and particle size of 500 microns with an external load of 3.0 kPa. Exchange of sulfobetaine with methacrylamide (SBAm), the main polymer backbone, revealed a positive increase in energy recovery of 670 J kg−1 with a mean power of 0.19 W kg−1 for the tandem system operating under the same parameters (SPA@SBAm). The energy recovery can be controlled, modulated and tuned by selecting both hydrogels with antipolyelectrolyte and polyelectrolyte effects and their performing parameters. This proof of concept provides blue energy harvesting by contributing both polyelectrolyte and antipolyelectrolyte effects in a single tandem setup; together with easy accessibility (diaper-based materials (SPA)) and known antibiofouling, these properties offer a robust alternative for energy harvesting.

Possible Treatment of Myocardial Infarct Based on Tissue Engineering Using a Cellularized Solid Collagen Scaffold Functionalized with Arg-Glyc-Asp (RGD) Peptide

Currently, the clinical impact of cell therapy after a myocardial infarction (MI) is limited by low cell engraftment due to low cell retention, cell death in inflammatory and poor angiogenic infarcted areas, secondary migration. Cells interact with their microenvironment through integrin mechanoreceptors that control their survival/apoptosis/differentiation/migration and proliferation. The association of cells with a three-dimensional material may be a way to improve interactions with their integrins, and thus outcomes, especially if preparations are epicardially applied. In this review, we will focus on the rationale for using collagen as a polymer backbone for tissue engineering of a contractile tissue. Contractilities are reported for natural but not synthetic polymers and for naturals only for: collagen/gelatin/decellularized-tissue/fibrin/Matrigel™ and for different material states: hydrogels/gels/solids. To achieve a thick/long-term contractile tissue and for cell transfer, solid porous compliant scaffolds are superior to hydrogels or gels. Classical methods to produce solid scaffolds: electrospinning/freeze-drying/3D-printing/solvent-casting and methods to reinforce and/or maintain scaffold properties by reticulations are reported. We also highlight the possibility of improving integrin interaction between cells and their associated collagen by its functionalizing with the RGD-peptide. Using a contractile patch that can be applied epicardially may be a way of improving ventricular remodeling and limiting secondary cell migration.

Structure Design for High Performance n-Type Polymer Thermoelectric Materials

Organic thermoelectric (OTE) materials have been regarded as a potential candidate to harvest waste heat from complex, low temperature surfaces of objects and convert it into electricity. Recently, n-type conjugated polymers as organic thermoelectric materials have aroused intensive research in order to improve their performance to match up with their p-type counterpart. In this review, we discuss aspects that affect the performance of n-type OTEs, and further focus on the effect of planarity of backbone on doping efficiency and eventually the TE performance. We then summarize strategies such as implementing rigid n-type polymer backbone or modifying conventional polymer building blocks for more planar conformation. In the outlook part, we conclude forementioned devotions and point out new possibility that may promote the future development of this field.

Vitrimerization of Poly(butylene succinate) By Reactive Melt Mixing Using Zn(II) Epoxy-Vitrimer Chemistry

Vitrimers constitute a new class of covalent adaptable networks (CANs), in which thermally stimulated associative exchange reactions allow the topological rearrangement of the dynamic network while keeping the number of bonds and the crosslink density constant. The current study proposed a solvent-free method to synthesize vitrimers by reactive melt mixing using a commercial biobased/biodegradable polyester, poly(butylene succinate), PBS. More specifically, a two-step process was followed; the first step involved reactive mixing of PBS with the crosslinker (diglycidyl ether of bisphenol A, DGEBA) and the transesterification catalyst (Zinc(II) acetylacetonate hydrate, Zn(acac)2) in a twin-screw mini-compounder, in order to incorporate the epoxy groups in the polymer backbone. The second step (vitrimerization) comprised a crosslinking process of the homogenous mixtures in a vacuum oven at 170 °C, resulting in the formation of a dynamic crosslinked network with epoxy moieties serving as the crosslinkers. By tuning the crosslinker content (0–10% mol with respect to PBS repeating unit) and the Zinc(II) catalyst to crosslinker ratio (0 to 1), tailor-made vitrimers were prepared with high insolubility and improved melt strength. Moreover, PBS vitrimers could still be reprocessed by compression molding after the crosslinking, which enables the recycling process. This work was made possible by the “Basic Research Programme, NTUA, PEVE 2020 NTUA” [PEVE0050] of the National Technical University of Athens and is gratefully acknowledged.

Biobased Waterborne Polyurethane-Ureas Modified with POSS-OH for Fluorine-Free Hydrophobic Textile Coatings

Waterborne polyurethane-urea dispersions (WPUD), which are based on fully biobased amorphous polyester polyol and isophorone diisocyanate (IPDI), have been successfully synthesized obtaining a finishing agent that provides textiles with an enhanced hydrophobicity and water column. Grafting of trans-cyclohexanediol isobutyl POSS (POSS-OH) to the biobased polymer backbone has also been investigated for the first time and its properties compared to a standard chain extender, 1,3-propanediol (PDO). The chemical structure of WPUD has been characterized by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The thermal properties have been evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Mechanical properties have been studied by tensile stress–strain analysis. Moreover, the particle size, particle size distribution (PSD), and stability of developed waterborne dispersions have been assessed by dynamic light scattering (DLS), Z-potential, storage aging tests, and accelerated aging tests by analytical centrifuge (LUM). Subsequently, selected fabrics have been face-coated by the WPUD using the knife coating method and their properties have been assessed by measuring the water contact angle (WCA), oil contact angle (OCA), water column, fabric stiffness, air permeability, and water vapor resistance (breathability). Finally, the surface morphology and elemental composition of uncoated and coated fabrics have been studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), respectively. All of the synthesized polyurethane-ureas provided the coated substrates with a remarkable hydrophobicity and water column, resulting in a more sustainable alternative to waterproof coatings based on fluoropolymers, such as PTFE. Grafting POSS-OH to the polymeric backbone has led to textile coatings with enhanced hydrophobicity, maintaining thermal, mechanical, and water column properties, giving rise to multifunctional coatings that are highly demanded in protective workwear and technical textiles.

P01.07 Depletion of CD206high tumour-associated macrophages using a nanoconjugate limits tumour burden & dissemination in metastatic triple negative breast cancer in mice

BackgroundAnti-inflammatory (M2) tumour-associated macrophages (TAMs) exert protumoural roles through angiogenesis, immunosuppression and resistance to therapies.1 M2 TAMs express the mannose receptor, CD206,2 excellent marker for targeted therapies. We have previously identified a peptide called mUNO2 that specifically binds to CD206 on M2 TAMs. Aiming to dissect the role of CD206high M2 TAMs in the tumour progression and immunosuppression, we depleted them using an mUNO and doxorubicin (Adriamycin®)-containing polymer-drug nanoconjugate (St-PGA-DOX-mUNO, ‘OximUNO’) where the polymer backbone is branched polyglutamic acid (St-PGA).3Materials and MethodsWe compared OximUNO with free DOX and the untargeted nanoconjugate St-PGA-DOX. To study the in vitro cytotoxicity of the nanoconjugates, we used M2 and M1 skewed macrophages derived from human blood buffy coat. To study the in vivo homing of nanoconjugates we used an orthotopic triple negative breast cancer (TNBC, 4T1 cells) model and a TNBC experimental metastases model in immunocompetent mice. For in vivo therapeutic efficacy studies, we used orthotopic and experimental metastases models of TNBC, and administered the compounds intraperitoneally (i.p.).ResultsIn vitro, OximUNO showed 39% higher toxicity to the primary human M2 macrophages than St-PGA-DOX, and 31% lower toxicity to the M1 macrophages than St-PGA-DOX. In vivo, OximUNO showed no change in creatinine or alanine aminotransferase values, indicating no toxic effects to the kidneys or liver. Compared to control St-PGA, i.p.-administered St-PGA-mUNO, showed improved homing to M2 TAMs in both orthotopic and experimental metastases models with low accumulation in the liver. In the orthotopic treatment study, only OximUNO significantly reduced the tumour volume and showed 56% and 38% less lung metastases than DOX and St-PGA-DOX, respectively. Additionally, DOX and St-PGA-DOX produced a significant bodyweight loss whereas OximUNO did not. Importantly, OximUNO treatment resulted in 2-5-fold increase in the ratio of CD8+/FOXP3+ expression, suggesting a shift in the immune landscape towards an immunostimulatory profile. In the experimental metastases model, OximUNO monotherapy resulted in the highest reduction of lung metastases, and this effect correlated with a significant reduction in CD206high M2 TAMs; whereas no significant effect on M2 TAMs population was observed with DOX or untargeted nanoconjugate.ConclusionsOur data suggests that the elimination of CD206high M2 TAMs with OximUNO suppresses spontaneous and experimental metastases in safe manner, shifts immune landscape towards immunostimulatory and could therefore be a potential treatment option for TNBC patients.ReferencesHughes R, Qian B-Z, Rowan C, Muthana M, Keklikoglou I, Olson OC, et al. Perivascular M2 macrophages stimulate tumor relapse after chemotherapy. Cancer Res 2015;75(17):3479–91.Scodeller P, Simón-Gracia L, Kopanchuk S, Tobi A, Kilk K, Säälik P, et al. Precision targeting of tumor macrophages with a CD206 binding peptide. Sci Rep 2017;7(1):14655.Duro-Castano A, Nebot VJ, Niño-Pariente A, Armiñán A, Arroyo-Crespo JJ, Paul A, et al. Capturing ‘extraordinary’ soft-assembled charge-like polypeptides as a strategy for nanocarrier design. Adv Mater 2017;29(39):1702888.Disclosure InformationA. Lepland: None. A. Malfanti: None. U. Haljasorg: None. S. Dordevic: None. L. Salumäe: None. P. Peterson: None. T. Teesalu: None. M.J. Vicent: None. P. Scodeller: None.