Andreas Taden

Controlled Formation of Polymer Nanocapsules with High Diffusion‐Barrier Properties and Prediction of Encapsulation Efficiency

Polymer nanocapsules with high diffusion-barrier performance were designed following simple thermodynamic considerations. Hindered diffusion of the enclosed material leads to high encapsulation efficiencies (EEs), which was demonstrated based on the encapsulation of highly volatile compounds of different chemical natures. Low interactions between core and shell materials are key factors to achieve phase separation and a high diffusion barrier of the resulting polymeric shell. These interactions can be characterized and quantified using the Hansen solubility parameters. A systematic study of our copolymer system revealed a linear relationship between the Hansen parameter for hydrogen bonding (δh ) and encapsulation efficiencies which enables the prediction of encapsulated amounts for any material. Furthermore EEs of poorly encapsulated materials can be increased by mixing them with a mediator compound to give lower overall δh values.

Phosphonic Acid-Functionalized Polyurethane Dispersions with Improved Adhesion Properties

A facile route to phosphorus-functionalized polyurethane dispersions (P-PUDs) with improved adhesion properties is presented. (Bis)phosphonic acid moieties serve as adhesion promoting sites that are covalently attached via an end-capping reaction to isocyanate-reactive polyurethane particles under aqueous conditions. The synthetic approach circumvents solubility issues, offers great flexibility in terms of polyurethane composition, and allows for the synthesis of semicrystalline systems with thermomechanical response due to reversible physical cross-linking. Differential scanning calorimetry (DSC) is used to investigate the effect of functionalization on the semicrystallinity. The end-capping conversion was determined via inductively-coupled plasma optical emission spectroscopy (ICP-OES) and was surprisingly found to be almost independent of the stoichiometry of reaction, suggesting an adsorption-dominated process. Particle charge detection (PCD) experiments reveal that a dense surface coverage of phosphonic acid groups can be attained and that, at high functionalization degrees, the phosphonic adhesion moieties are partially dragged inside the colloidal P-PUD particle. Quartz crystal microbalance with dissipation (QCMD) investigations conducted with hydroxyapatite (HAP) and stainless steel sensors as model surfaces show a greatly enhanced affinity of the aqueous P-PUDs and furthermore indicate polymer chain rearrangements and autonomous film formation under wet conditions. Due to their facile synthesis, significantly improved adhesion, and variable film properties, P-PUD systems such as the one described here are believed to be of great interest for multiple applications, e.g., adhesives, paints, anticorrosion, or dentistry.

Dual-compartment nanofibres: separation of two highly reactive components in close vicinity

Dual-compartment nanofibres separating two highly reactive components in close vicinity are investigated. The study is intended as a non-classical approach for the control of reaction latency in colloidal systems. An epoxide resin and a hydrophobic polyamine which react readily at low temperatures are chosen as model compounds. Colloid electrospinning with PVA as the confining matrix is used for the immobilization of both in separate compartments. Uniform fibres are produced with a matrix/colloid weight ratio of 3/1. The internal fibre morphology was investigated via dual-colour stimulated emission depletion (STED) microscopy and TEM. The results show a statistical distribution of epoxy- and amine-containing compartments and indicate average particle–particle distances of <100 nm, which is supported by computations. The fibres are highly storage stable under ambient conditions and yet allow for efficient crosslinking and self-healing. The curing reaction can be initiated via thermal or mechanical stimuli, as demonstrated by electron microscopy and electrochemical testing of fibre containing coatings. The reactivity and latency for reaction is furthermore proven by calorimetric and chromatographic methods.

Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks†

Photopolymers with unique curing capabilities were produced by combining living cationic polymerization with network formation and restricted polymer motion. A vinyl ether diol was synthesized as a functional building block and reacted with isophorone diisocyanate to form a highly functionalized vinyl ether polyurethane as a model system with high crosslinking ability. When using a cationic photoinitiator, fast polymerization is observed upon short UV irradiation. Curing proceeds in the absence of light and under ambient conditions without oxygen inhibition. Cationic active sites become trapped dormant species upon network-induced vitrification and surprisingly remain living for several days. The polymerization can be reactivated by additional UV irradiation and/or raised temperature. The curing behavior was studied in detail by using UV and FT-NIR coupled rheology and photo-DSC to simultaneously study spectroscopic and mechanical information, as well as thermal effects.

Polyurethane Dispersions with Peptide Corona: Facile Synthesis of Stimuli-Responsive Dispersions and Films

Peptide-polymer hybrid particles of submicron size yielding stimuli-responsive macroscopic films are presented. A thermoplastic polyurethane (PU) carrying polysiloxane and polyester soft segments serves as core material to obtain flexible, yet semicrystalline films with temperature-sensitivity. The synthesis is based on the high-sheer emulsification of isocyanate-terminated PU prepolymers, which in our model system purposefully lack any ability of colloidal self-stabilization. While emulsification in water leads to immediate coagulation, stable dispersions of polyurethane nanoparticles were formed in aqueous solutions of a hydrolyzed protein from wool. A comparison of dispersion and film properties to nonreactive, otherwise identical dispersions suggests covalent attachment of the peptide to the PU backbone. We show that the colloidal stability of the hybrid particles is completely governed by the peptide corona, and hence pH-triggered coagulation can be employed to induce particle deposition and film formation. Differential scanning calorimetry confirms partial crystallinity in the film and reveals strongly modified crystallization behavior due to the peptide.

Benzoxazines for Industrial Applications Comparison with Other Resins, Formulation and Toughening Know-How, and Water-Based Dispersion Technology

Publisher Summary The promising family of benzoxazines is developed by academia and industry as a new type of phenolic resins, which can potentially open up new applications and product opportunities. Due to the molecular design flexibility of benzoxazines, certain desired properties can be tailored. For most customers or end-users the underlying chemical structures or physical principles are only of secondary importance. Due to the advantages of benzoxazines, it is expected that the use of benzoxazines will grow significantly in the future and become an important part in general industry. The synthesis of benzoxazines can be performed with or without solvents. The industrial application of benzoxazine resins, these oligomers often prove to be beneficial in several ways. In this chapter the general properties of benzoxazines with various other thermosetting materials like standard phenolic resins, BMI, and epoxides are compared. All its aspects are described with an emphasis on the methodology of research activities. Special focus is laid on the toughening additives. The chapter explains efforts to extent the area of benzoxazine research to the field of water-based dispersions. Polymerizable nonionic benzoxazine surfactants and two different types of polymerizable benzoxazine based protective colloids are developed that can effectively stabilize different benzoxazine-based formulations as small droplets in water. The described benzoxazine containing surface-active stabilizers have the strong advantage that they can seamlessly copolymerize and become an integral part of a polybenzoxazine network upon curing.

How to capture the bioeconomy’s industrial and regional potential through professional cluster management

The bioeconomy transforms the fossil-based economy by forming new value chains and linking until now distinct industrial sectors. It provides an opportunity for rural as well as industrialized regions. The transformation process can be accelerated by building bioeconomy clusters comprising industries, academia and investors. Using the model of the German cluster CLIB2021 the role of cluster organisations and professional cluster management in moderating the transformation process and gaining a competetive advantage is discussed. In addition examples of how cluster management supports the formation of an industrial consortium and the analysis of regional options are presented.

A Nanocapsule-Based Approach Toward Physical Thermolatent Catalysis.

Performance under pressure is utilized as a key concept for colloidal control of reaction kinetics. Barrier nanocapsules containing a catalyst and a low-boiling-point release agent enable a highly desired, adjustable, and distinct non-Arrhenius behavior for thermoset curing.

Water-Based Adhesives with Tailored Hydrophobic Association: Dilution Resistance and Improved Setting Behavior

Hydrophobic association and stimuli-responsiveness is a powerful tool towards water-based adhesives with strongly improved properties, which is demonstrated based on the example of hydrophobically modified alkali-soluble latexes (HASE) with modulated association. Their rheological properties are highly tunable due to the hydrophobic domains that act as physical crosslinking sites of adjustable interaction strength. Ethanol, propanol, and butanol are used as water-soluble model additives with different hydrophobicity in order to specifically target the association sites and impact the viscoelastic properties and stimuli-responsiveness. The rheological and mechanical property response upon dilution with water can be tailored, and dilution-resistant or even dilution-thickening systems are obtained. The investigations are of high importance for water-based adhesives, as our findings provide insight into general structure-property relationships to improve their setting behavior, especially upon contact with wet substrates.