Macromolecular Materials and Engineering

Cover: Electrospun PLLA/PEG shell/core fibers were collected and deposited in series to form ‘standing’ membranes. After washing away PEG, a highly aligned, single-layered, hollow, fibrous PLLA membrane was obtained. High-speed videography captured its epitaxial growth and SEM revealed hundreds of microscale hollow fibers, arranged in connected, parallel monolayers, forming an ordered, 2D microtube array (MTA). By adjusting the applied field strength and solution viscosity, an operational map was constructed and validated independently. A 5x30 cm² MTA membrane could be prepared. These membranes are easy to manipulate into various configurations and their ability to mimic several anisotropic tissue structures make them an excellent candidate for tissue engineering scaffolds. Further details can be found in the article by J.-C. Yang, S.-Y. Lee, W.-C. Tseng, Y.-C. Shu, J.-C. Lu, H.-S. Shie, and C.-C. Chen* on page 115.

Novel super-aligned, single-layered, PLLA hollow fibrous membranes are prepared via coaxial electrospinning. The formation mechanism is investigated using high-speed video to demonstrate the epitaxial-like packing of the electrospun core/shell fibers. A working map is constructed and verified for precision fabrication of such unique structures of mono-layered µm-sized hollow fiber arrays.

Highly conductive P3HT fibers are prepared via melt spinning of P3HT followed by fiber drawing and doping with FeCl₃. Alternatively, PET fibers were coated with P3HT and the resulting fibers were drawn to yield conductive fibers. The amount of crystalline phases can be significantly increased during the spinning process and enhanced even further by drawing.

Copolymers of trimethylene carbonate and L-lactide are synthesized with TMC/LLA ratios of 1/3, 1/4, and 1/5. A composite is fabricated from PTL15 matrix reinforced with PLGA short fibers. In vitro degradation of the copolymers, composite, and poly(L-lactide) shows that the composite degrades most rapidly because the faster degradation of PLGA fibers speeds up the degradation of the matrix by internal autocatalysis.

Reactively compatibilized PVDF/TPU 90/10 and 10/90 blends with different concentrations of PVDF-g-AAc are prepared. The rheological behavior of the compatibilized blends can be described by a generalized Zener model. They can be characterized by a particle-dispersed type of morphology, and the dispersed-phase domain size decreases significantly with the increase in compatibilizer concentration.

A series of poly(arylene ether phosphine oxide)s are prepared from a new phosphorus-containing bisfluoro monomer. In addition to very good thermal stability and high char residue, the polymers show very low heat release in the microscale combustion calorimeter test. Transparent thin films of these polymers show good mechanical properties and hydrophobicity with water contact angles above 91°.

Low-stress hyperbranched polymer/silica nanostructures are produced using either a dual-cure sol/gel and photopolymerization process or by solvent-assisted mixing with nanoparticles. Optimization of the dual-cure process leads to transparent sol/gel composites with ultrafine structures and internal stress levels as low as 2.5MPa. These sol/gel composites are used to accurately replicate nanoscale patterns.

Factorial design analyses and numerical optimization are performed to establish material compositions (wood flour content, particle size, and impact modifier content) and mechanical property relationships for PLA/wood flour composites. Strategies are developed to manufacture cost-effective PLA/wood flour composites with impact and tensile properties similar to those of unfilled PLA.

Gelling-agent-fortified SPC-based biodegradable films are described and their mechanical strengths, thermal stabilities, and moisture resistances are characterized. When the ratio of SPC and gelling agents is balanced, IPN-like structures form and the strength, stiffness, glass transition temperature, and moisture resistance of the films are significantly improved.

PP/soy fiber and PHBV/PLA/soy fiber composites are prepared and their thermal, mechanical, and morphological properties are studied. Stress and the strain at failure of all composites decrease with increasing soy fiber content. Compatibilized composites show higher flexural and impact strength than the noncompatibilized ones. Compatibilization reduces moisture uptake by the composites significantly.