Electrospun and in situ self-polymerization of polyacrylonitrile containing gadolinium nanofibers for thermal neutron protection

In this work, the polyacrylonitrile containing gadolinium nanofibers for thermal neutron protection were successfully fabricated by electrospunning and followed by in situ self-polymerization. Scanning electron microscopy(SEM) and energy-dispersive spectroscopy(EDS) results show that there are no beads on the smooth surface of the nanofibers and gadolinium elements are uniformly dispersed in the matrix. The thermal analysis and FTIR results prove that gadolinium methacrylate is induced in situ selfpolymerization during the heat treatment. The leaching rate of Gd^(3+) decreases from 79.97% to 10.74% tested by lowfield nuclear magnetic resonance(LF-NMR) method after the self-polymerization of gadolinium methacrylate in the matrix when the nanofibers were immersed in water for7 days. The thermal neutron shielding analysis calculated by MCNP program shows that above 99% thermal neutrons are absorbed when traveling through the 2-mm-thick polyacrylonitrile containing gadolinium nanofibers.

Self-polymerization of Eu(TTA)_3AA in rubber and their fluorescence effect

A simple europium complex,Eu（TTA）3 AA（TTA=4,4,4-trifluoro-1-（2-thienyl）-1,3-butanedione,AA=acrylic acid） was synthesized by a simple solution method.Then,two kinds of rubber matrix,nitrile-butadiene rubber（NBR） and silicone rubber（SiR） were used as the substrate for Eu（TTA）3 AA to prepare fluorescence composites.The neat Eu（TTA）3 AA complex showed the ability of self-polymerization when it was heated at 145 °C.It was found that the fluorescence intensity of the neat Eu（TTA）3 AA decreased over 70% when the polymerization time was over 25 min at 145 °C.The results also revealed that the polymerizated Eu（TTA）3 AA could be dispersed in nano-scale in two matrices and the luminescent intensities decreased 52% in NBR matrix,and 95% in SiR matrix compared with two relative compounds without crosslinking.To optimize the luminescence intensity of the composites,the Eu（TTA）3 AA polymerization kinetic process in matrix was investigated in detail by controlling the temperature,the crosslinking agent,etc.The results showed that the peroxide could accelerate Eu（TTA）3 AA self-polymerization in the rubber matrix,and therefore improved the dispersion,but not be helpful for the luminescence intensity enhancement.In addition,the relatively higher luminescence intensity in Eu（TTA）3 AA/NBR in comparison to that of Eu（TTA）3 AA/SiR might contribute to the interaction between nitrile group（–CN） in NBR and Eu-complexes,suggesting that the luminescence intensity of the composites also depended on the matrix characteristics.

HYDROPHILIC NANOFILTRATION MEMBRANES WITH SELF-POLYMERIZED AND STRONGLY-ADHERED POLYDOPAMINE AS SEPARATING LAYER

Inspired by the self-polymerization and strong adhesion characteristics of dopamine in aqueous conditions, a novel hydrophilic nanofiltration （NF） membrane was fabricated by simply dipping polysulfone （PSf） ultrafiltration （UF） substrate in dopamine solution. The changes in surface chemical composition and morphology of membranes were determined by Fourier transform infrared spectroscopy （FTIR-ATR）, X-ray photoelectron spectroscopy （XPS）, scanning electron microscopy （SEM） and atomic force microscopy （AFM）. The experimental results indicated that the self-polymerized dopamine formed an ultrathin and defect-free barrier layer on the PSf UF membrane. The surface hydrophilicity of membranes was evaluated through water contact angle measurements. It was found that membrane hydrophilicity was significantly improved after coating a polydopamine （pDA） layer, especially after double coating. The dyes filtration experiments showed that the double-coated membranes were able to reject completely the dyes of brilliant blue, congo red and methyl orange with a pure water flux of 83.7 L/（mE.h） under 0.6 MPa. The zeta potential determination revealed the positively-charged characteristics of PSf/pDA composite membrane in NF process. The salt rejection of the membranes was characterized by 0.01 mmol/L of salts filtration experiment. It was demonstrated that the salts rejections followed the sequence： NaC1 〈 NaaSO4 〈 MgSO4 〈 MgC12 〈 CaCl2, and the rejection to CaC12 reached 68.7%. Moreover, the composite NF membranes showed a good stability in water-phase filtration process.

Reductant-assisted polydopamine-modified membranes for efficient water purification

Surface engineering with polydopamine coatings has been considered a promising surface functionalisation tool.However,it is difficult to control the self-polymerisation for polydopamine formation,which usually causes severe interparticle aggregation.In this study,polydopamine self-polymerisation was controlled by adjusting its reducing environment using a reductant(NaBH4)to fabricate mixed cellulose ester(MCE)/polydopamine membranes.An oxidising environment using NaIO4 was additionally tested as the control.The results showed that a thin polydopamine coating with small polydopamine particles was formed on the skeleton frameworks of the MCE membrane with NaBH4,and the self-polymerisation rate was suppressed.The polydopamine coating formed in the reducing environment facilitated excellent water transport performance with a water permeance of approximately 400 L·m^(−2)·h^(−1)·bar^(−1) as well as efficient organic foulant removal with a bovine serum albumin rejection of approximately 90%.In addition,the polydopamine coating with NaBH4 exhibited both excellent chemical stability and anti-microbial activity,demonstrating the contribution of the reducing environment to the performance of the MCE/polydopamine membranes.It shows significant potential for use in water purification.

Poly-dopamine, poly-levodopa, and poly-norepinephrine coatings: Comparison of physico-chemical and biological properties with focus on the application for blood-contacting devices

Thanks to its simplicity,versatility,and secondary reactivity,dopamine self-polymerized coatings(pDA)have been widely used in surface modification of biomaterials,but the limitation in secondary molecular grafting and the high roughness restrain their application in some special scenarios.Therefore,some other catecholamine coatings analog to pDA have attracted more and more attention,including the smoother poly-norepinephrine coating(pNE),and the poly-levodopa coating(pLD)containing additional carboxyl groups.However,the lack of a systematic comparison of the properties,especially the biological properties of the above three catecholamine coatings,makes it difficult to give a guiding opinion on the application scenarios of different coatings.Herein,we systematically studied the physical,chemical,and biological properties of the three catecholamine coatings,and explored the feasibility of their application for the modification of biomaterials,especially cardiovascular materials.Among them,the pDA coating was the roughest,with the largest amount of amino and phenolic hydroxyl groups for molecule grafting,and induced the strongest platelet adhesion and activation.The pLD coating was the thinnest and most hydrophilic but triggered the strongest inflammatory response.The pNE coating was the smoothest,with the best hemocompatibility and histocompatibility,and with the strongest cell selectivity of promoting the proliferation of endothelial cells while inhibiting the proliferation of smooth muscle cells.To sum up,the pNE coating may be a better choice for the surface modification of cardiovascular materials,especially those for vascular stents and grafts,but it is still not widely recognized.

Hydrogen bond-induced elastic polyzwitterion electrolytes constructed by mussel-inspired autopolymerization for zinc-ion battery

Aqueous zinc-ion batteries(ZIBs)have attracted much interest to realize safe rechargeable batteries with high safety and high energy density.However,it is still challenging to address dendrite growth and parasitic reactions in zinc anodes.We propose herein the design concept of hydrogen bond-induced elastic polyzwitterion electrolytes with zincophilic groups for achieving robust ZIBs.Mussel-inspired autopolymerization has been developed to construct the polyzwitterion electrolytes at room temperature by inducing electron density delocalization atα-position of C=C bond in zwitterion monomer by Zn^(2+).Specifically,the zwitterionic functional groups construct ion transport channels,and the unique–NH–and SO_(3)^(-)groups co-compete with H_(2)O for coordination with Zn^(2+)and promote the desolvation of hydrated Zn^(2+),thus achieving a high room temperature ionic conductivity(6.7 mS cm^(-1))and an increased Zn^(2+)migration number(0.65)for the polyzwitterion electrolytes.In addition,various interactions such as hydrogen bonding and electrostatic interactions between electrolyte ions and zwitterionic groups impart high stretchability and strength to the polyzwitterion electrolytes,which,combined with SO_(3)^(-)philic(002)crystallographic properties,effectively inhibit the growth of zinc dendrites.As a result,rigid/wearable solid-state ZIBs exhibit excellent cycling and C-rate performances.We believe that the strategy of constructing polyzwitterionic electrolytes with zincophilic groups and ion transport channels opens up a new direction in polymer electrolyte engineering towards safe and high energy batteries.