Preparation of Homopolymer, Block Copolymer, and Patterned Brushes Bearing Thiophene and Acetylene Groups Using Microliter Volumes of Reaction Mixtures

The synthesis of surface-grafted polymers with variable functionality requires the careful selection of polymerization methods that also enable spatially controlled grafting, which is crucial for the fabrication of, e.g., nano (micro) sensor or nanoelectronic devices. The development of versatile, simple, economical, and eco-friendly synthetic strategies is important for scaling up the production of such polymer brushes. We have recently shown that poly (3-methylthienyl methacrylate) (PMTM) and poly (3-trimethylsilyl-2-propynyl methacrylate) (PTPM) brushes with pendant thiophene and acetylene groups, respectively, could be used for the production of ladder-like conjugated brushes that are potentially useful in the mentioned applications. However, the previously developed syntheses of such brushes required the use of high volumes of reagents, elevated temperature, or high energy UV-B light. Therefore, we present here visible light-promoted metal-free surface-initiated ATRP (metal-free SI-ATRP) that allows the economical synthesis of PMTM and PTPM brushes utilizing only microliter volumes of reaction mixtures. The versatility of this approach was shown by the formation of homopolymers but also the block copolymer conjugated brushes (PMTM and PTPM blocks in both sequences) and patterned films using TEM grids serving as photomasks. A simple reaction setup with only a monomer, solvent, commercially available organic photocatalyst, and initiator decorated substrate makes the synthesis of these complex polymer structures achievable for non-experts and ready for scaling up.

Synthesis of Low Temperature Resistant Hydrogenated Nitrile Rubber Based on Esterification Reaction

Hydrogenated Nitrile Rubber (HNBR) is widely used in aerospace, petroleum exploration and other fields because of its excellent performances. However, there remains a challenge of balancing the oil resistance and the low temperature resistance for HNBR. In this work, a series of grafted carboxyl nitrile rubber (XNBR) was prepared by the esterification reaction between active functional groups (–COOH) of XNBR and alkanols of different molecular chain lengths (C8H17OH, C12H25OH, C16H33OH, C18H37OH) or Methoxypolyethylene glycols (MPEG) of different molecular weights (Mn = 350, 750, 1000). The structure and low temperature resistance of as-obtained grafted polymers were characterized by Fourier Transform Infrared (FTIR), 1H-NMR and Differential scanning calorimetry (DSC). It was found that the glass transition temperatures (Tg) of grafted XNBR were significantly decreased. MPEG grafted polymers with better low temperature resistance were then selected for hydrogenation. As-prepared hydrogenated XNBR grafted with MPEG-1000 (HXNBR-g-1000) showed the lowest Tg of −29.8 °C and the best low temperature resistance. This work provides a novel and simple preparation method for low temperature resistant HNBR, which might be used potentially in extremely cold environments.

Delivery and Diffusion of Retinal in Dermis and Epidermis Through The Combination of Prodrug Nanoparticles and Detachable Dissolvable Microneedles

To minimize fast chemical degradation of retinal, we convert this aldehyde into proretinal nanoparticles (PRNs) by forming retinylidene moieties on chitosan and allowing the grafted polymers to assemble into nanoparticles, and then load the obtained PRNs into detachable microneedles made of 1:1 (by weight) hyaluronic acid/maltose. An embedment of the PRNs in the solid matrix of microneedles helps improving chemical stability of the grafted retinal; the loaded device can be kept at 25 °C for three months (longest time experimented) with less than 30% degradation of the retinylidene moieties. The presence PRNs in the hyaluronic acid-maltose matrix also help improving mechanical strength of the needles. Administration of PRN-loaded detachable microneedles on fresh porcine ear skin results in complete deposition of an array of microneedles in the skin tissue at the dept that spans both epidermis and dermis, as observed by stereomicroscopic and confocal fluorescence microscopic analyses of the cross-sectioned tissue pieces. Obvious diffusion of the PRNs from the originally embedded site of the needles in the skin tissue to the nearby location can be observed, and even distribution in the tissue is reached at 4 h post administration. Rats administered with single dose of PRN-loaded microneedles show significant increased epidermal thickness as compared to rats administered with unloaded microneedles. Both PRN-loaded microneedles and unloaded microneedles produce no skin irritation in rats.

Biological macromolecule chitosan grafted co-polymeric composite: bio-adsorption probe on cationic dyes

Chitosan biological macromolecule is a versatile polymer; chemical modification has been carried out that lead to the formation of chitosan grafted polymers composites (Chito-g-PC). We proposed synthesis of six various Chito-g-PC as sorbents for toxic dyes. A novel graft copolymerization method based on radical polymerization with vinyl monomer like acrylic acid, acrylamide, N-isopropylacrylamide, methacrylic acid and polyacrylonitrile were utilized in order to address the large amount of swelling at four different pH buffers solution. The effect of initiator and monomer concentration, time and temperature on % grafting and % grafting efficiency were performed. Comparative characterization of Chito and Chito-g-PC were evaluated by SEM, XRD and FTIR, as well as solubility characteristics of the composites were determined by various pH buffer solution. Cationic toxic dyes Malachite green (MG) and Methylene blue (MB) were selected as the sorbet, and Chito-g-PC were used as biosorbents. Thermodynamic analysis showed that the sorption process was spontaneous and endothermic with an increased randomness. The sorption experiments were realized with six different Chito-g-PC for MG and MB at various pH.

Atomic Force Microscopy Characterization of Biomaterials Modified with Poly(styrene Sulfonate)

<p>Polycaprolactone and polyethylene terephthalate are widely used to elaborate biomaterials and medical devices in particular for long-term implant applications but tuning their surface properties remains challenging. We investigate surface functionalization by grafting poly(sodium 4-styrene sulfonate) with the aim of enhancing protein adhesion and cellular activity. Elucidating the topography and molecular level organization of the modified surfaces is important for understanding and predicting biological activity. In this work, we explore several grafting methods including thermal grafting, thermal grafting in the presence of Mohr's salt, and UV activation. We characterize the different surfaces obtained using atomic force microscopy, contact angle and X-ray photoelectron spectroscopy. The results reveal striking differences in the properties of the modified surfaces. This work demonstrates tuning of biomaterials surface by functionalization and the capability of atomic force microscopy to provide insights into the conformation and mechanical properties of the grafted polymers. </p>

Atomic Force Microscopy Characterization of Biomaterials Modified with Poly(styrene Sulfonate)

<p>Polycaprolactone and polyethylene terephthalate are widely used to elaborate biomaterials and medical devices in particular for long-term implant applications but tuning their surface properties remains challenging. We investigate surface functionalization by grafting poly(sodium 4-styrene sulfonate) with the aim of enhancing protein adhesion and cellular activity. Elucidating the topography and molecular level organization of the modified surfaces is important for understanding and predicting biological activity. In this work, we explore several grafting methods including thermal grafting, thermal grafting in the presence of Mohr's salt, and UV activation. We characterize the different surfaces obtained using atomic force microscopy, contact angle and X-ray photoelectron spectroscopy. The results reveal striking differences in the properties of the modified surfaces. This work demonstrates tuning of biomaterials surface by functionalization and the capability of atomic force microscopy to provide insights into the conformation and mechanical properties of the grafted polymers. </p>