Type I collagen-PEO fibers and non-woven fiber networks were produced by the electrospinning of a weak acid solution of purified collagen at ambient temperature and pressure. As determined by high-resolution SEM and TEM, fiber morphology was influenced by solution viscosity, conductivity, and flow rate. Uniform fibers with a diameter range of 100-150 nm were produced from a 2-wt% solution of collagen-PEO at a flow rate of 100 μl min-1. Ultimate tensile strength and elastic modulus of the resulting non-woven fabrics was dependent upon the chosen weight ratio of the collagen-PEO blend. 1H NMR dipolar magnetization transfer analysis suggested that the superior mechanical properties, observed for collagen-PEO blends of weight ratio 1 : 1, were due to the maximization of intermolecular interactions between the PEO and collagen components. The process outlined herein provides a convenient, non-toxic, non-denaturing approach for the generation collagen-containing nanofibers and non-woven fabrics that have potent...

Engineered collagen-PEO nanofibers and fabrics.

The study of amphiphilic polymer based functional organic−inorganic hybrid materials is an emerging research area offering enormous scientific and technological promise. Here, we show that employing poly(isoprene-block-ethylene oxide) block copolymers (PI-b-PEO) and a silicon precursor, which contains a polymerizable organic moiety, unprecedented morphology control on the nanoscale is obtained. This control is based on a unique polymer−ceramic interface, which is characterized using a multi-nuclei solid-state NMR approach. The results show that the hydrophilic parts of the polymer are completely integrated into the ceramic phase, thereby leading to a quasi “two-phase system”, allowing for a more rational hybrid morphology design based on the current understanding of the phase behavior of block copolymers and copolymer−homopolymer mixtures. Examination of the full phase space of the hybrid materials reveals the existence of a new bicontinuous cubic structure that was not known to exist in polymer systems. ...

Block Copolymer−Ceramic Hybrid Materials from Organically Modified Ceramic Precursors

Production of objects with varied mechanical properties is challenging for current manufacturing methods. Additive manufacturing could make these multimaterial objects possible, but methods able to achieve multimaterial control along all three axes of printing are limited. Here we report a multi-wavelength method of vat photopolymerization that provides chemoselective wavelength-control over material composition utilizing multimaterial actinic spatial control (MASC) during additive manufacturing. The multicomponent photoresins include acrylate- and epoxide-based monomers with corresponding radical and cationic initiators. Under long wavelength (visible) irradiation, preferential curing of acrylate components is observed. Under short wavelength (UV) irradiation, a combination of acrylate and epoxide components are incorporated. This enables production of multimaterial parts containing stiff epoxide networks contrasted against soft hydrogels and organogels. Variation in MASC formulation drastically changes the mechanical properties of printed samples. Samples printed using different MASC formulations have spatially-controlled chemical heterogeneity, mechanical anisotropy, and spatially-controlled swelling that facilitates 4D printing. Objects with varied mechanical properties can be produced by additive manufacturing, but multimaterial control along all three axes of printing is still limited. Here the authors use wavelength control during vat polymerization and demonstrate printing of objects with spatial control of the composition and stiffness.

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Multimaterial actinic spatial control 3D and 4D printing

Proton spin diffusion for spatial heterogeneity and morphology investigations of polymers

The local chemical environments, dynamic heterogeneities, and nature of the interface in structured organic−inorganic composites prepared from poly(isoprene-b-ethyleneoxide) block copolymers, (3-glycidyloxypropyl)trimethoxysilane, and aluminum sec-butoxide via a sol−gel process are characterized by solid-state NMR Such composites self-assemble into the characteristic morphologies of block copolymer systems, with the inorganic component selectively swelling the poly(ethylene oxide) phases Here it is shown that the local chemical structure of the aluminosilicate component is nearly unperturbed by addition of the block copolymer and that the combined aluminosilicate/poly(ethylene oxide) layer is significantly less mobile than the polyisoprene Spin-diffusion measurements on a composite with lamellar morphology indicate that no significant (>1 nm thick) poly(ethylene oxide) interphase exists between the polyisoprene and poly(ethylene oxide)/aluminosilicate layers, and therefore, the inorganic and poly(ethyl

Structure, Mobility, and Interface Characterization of Self-Organized Organic-Inorganic Hybrid Materials by Solid-State NMR

Cationic UV-polymerized resins, based on cycloaliphatic epoxides with aryl sulfonium salts as photoinitiators and polypropylene glycols of variable length as flexibilizers, have been investigated with respect to the network-forming reactions and the morphology of the resulting polymers. The combination of UV-curing and thermal postcure makes the chemical process complex and dependent on many variables, such as photoinitiator, exposure time, reaction temperature, and polyol components. Structure and curing of the epoxide were investigated by 13C CPMAS NMR. Morphology and domain sizes were studied by spin diffusion experiments using the novel “dipolar filter” technique for selective magnetization of mobile components.

B. Stapp

Papers

Solid state NMR investigation of cationic polymerized epoxy resins