Ultraporous Nanosheath Materials by Layer‐by‐Layer Deposition onto Co‐continuous Polymer‐Blend Templates

Abstract

Porous polymer materials with interconnected porosity have recently received great attention due to their wide range of possible applications and the challenges they pose in preparation. Their potential applications range from use in the biomedical and pharmaceutical fields (tissue engineering and drug delivery) [1][2][3] to chromatographic materials, [4] to catalysis of chemical and biochemical reactions, [5] and to electronic devices.[6] For tissue-engineering applications, for instance, at least four different techniques for fabricating interconnected porous polymer substrates have been developed: fiber bonding of unwoven meshes, [7] solvent casting/particulate leaching, [8] gas foaming, [9] and phase separation.[10] However, every one of these approaches suffers from severe limitations including low levels of interconnectivity, low void volume, poor control of pore size and distribution, and difficulties in obtaining materials of reproducible porosities. Previously, we advanced an approach to preparing microporous materials based on the melt-blending of two immiscible polymers [11] and demonstrated that selective extraction of one of two components in a co-continuous mixture can result in a single-component structure of fully interconnected porosity with highly controlled porosity, morphology, and pore diameters ranging from 100 nm to hundreds of micrometers. [12,13] However, this method was found to be limited in the void volume that can be attained, and able to be used to prepare only relatively low-void-volume substrates (75 %). Layer-by-layer (LbL) deposition is a simple and effective approach to deposit ultrathin and uniform molecular layers onto surfaces in which polyelectrolytes are adsorbed on an oppositely charged surface, reversing the surface charge and leaving it primed for the next deposition cycle. [14][15][16] Originally exclusively investigated on macroscopically flat surfaces, this technique has been recently used to fabricate hollow spheres by assembling multilayered films onto colloidal particles and subsequently removing the core.[17] Hollow micro-and nanoparticles have also been prepared by removing the core of different crosslinked polymer brush surface-modified particles. [18,19] Macromolecular self-assembly techniques such as block-copolymer templates have already been used to prepare porous materials, [20,21] but to date no work has been reported on the use of LbL techniques to create 3D fully interconnected substrates.Here we report the use of LbL deposition onto a porous co-continuous blend template as a novel route towards ultrahigh-void-volume materials of high internal surface and closely controlled pore size. As an illustrative case, we selected bovine serum albumin (BSA) as a bioactive compound to be incorporated in the protocol. The present process is shown in Figure 1.First, co-continuous poly(L-lactic acid)/poly(e-caprolactone) (PLLA/PCL 50:50 wt.-%) blends are produced via melt-processing. In order to demonstrate the preparation of materials of different pore sizes, two pre...

Selective Localization of Nanofillers: Effect on Morphology and Crystallization of PLA/PCL Blends

“…Therefore, the PLA/ PCL blend materials have received much attention in recent years. [3][4][5][6][7][8][9][10][11][12] However, most polymer pairs are immiscible thermodynamically because of their unfavorable interactions, including PLA and PCL. The macrophase separation and the poor interfacial adhesion, as a result, highly restrict property combinations between PLA and PCL in their blend.…”

Fabrication of covalently linked PAH/PVS layer-by-layer assembled multilayers via a post-photochemical cross-linking strategy

“…Currently, the LbL technique has attracted tremendous attention for its simplicity, universality and precise control of thickness at the nanoscale, and has been widely applied in various promising research areas, including chemical sensors and biosensors [4] , stimuli-responsive micelles [5] , enzyme immobilization [6] , surface patterning [7][8][9] , controlled drug release systems [10] , photoelectrochemically active electrodes [11] , separation membranes [12] , microporous films [13] , surface-imprinted multilayers [14] , erasable films [15,16] and even macroscopic supramolecular assembly [17] . However, LbL assembled multilayers have been traditionally fabricated based on the weak electrostatic attraction of the interlayers [18][19][20] and the driving force of supramolecular interactions or other weak intermolecular interactions, which are unstable in some rigorous situations, such as high/low pH values, high ionic strength conditions or solutions with disturbances, for example under sonication [2] .…”

Development of a Porous Scaffold-Manufacturing Method by Blending Silk Fibroin and Agarose Polymer Solutions

“…Sarazin et al (2003;2004) developed a novel method for the generation of ultra-porous scaffolds by melt blending 2 or 4 immiscible polymers (Virgilio et al, 2010). Roy et al (2006) deposited polymer/ protein layers onto scaffold surfaces to increase the porosity of the materials. Virgilio et al (2005; and Horiuchi et al (1997) reported partial wetting in a significant number of scaffolds generated by ternary immiscible polymers blends.…”