Xiaoyu Li

Simultaneously increasing mechanical strength, toughness, thermal stability, and flame retardancy of epoxy thermoset without compromising transparency is appealing but challenging. To address that goal, a Schiff base epoxy VDEP is developed. The neat VDEP‐cured product, VDEP_100wt%, not only shows comparable mechanical strength to conventional epoxy thermoset but also can be degraded in 10% H₂SO₄/THF/H₂O solution in 24 h, showing great degradability under mild conditions. More importantly, proper addition of VDEP simultaneously increases the tensile strength, impact strength, T _g, T _d5%, char residue, and UV shielding of cured epoxies while providing self‐extinguishing ability. All of those enhancements are achieved without deteriorating transparency. When 15 wt% of VDEP is added, the tensile strength reaches 91.07 MPa, with a 36.7% increase; the impact strength reaches 40.73 kJ m⁻², with a 33.8% increase. The enhancement in mechanical strength is due to the reinforcing effect of intermolecular interaction and compacted network caused by free volume reduction. The higher toughness results from greater mobility of chain segments, reduced crosslinking density and energy dissipative intermolecular interaction. The rigid two benzene‐conjugated Schiff base structure and abundant hydrogen bonding contribute to higher T _g. Therefore, this work provides a degradable Schiff base epoxy and high‐performance thermoset based on it.

Bio‐based bisphenols from Hou Po (Cortex Magnoliae Officinalis, one of the popularly used herb in traditional Chinese medicine) was applied as a new kind of the chain extender for the synthesis of cationic waterborne polyurethane (CWPU). Since the representative Hou Po‐bisphenols include magnolol (MAG), honokiol (HON) and Magnolia officinalis extract (MPE), to explore their subtle structure effects and distinguish them from their petrochemical analogs of bisphenol A (BPA) and 2,2′‐biphenol (OBP), the CWPU modified by different bisphenols were systematically characterized and compared. It has been found that the copolymerization of MAG onto the backbone of CWPU can give out superior film toughness, damping factors and self‐healing efficiency (>90%). The elastic film recovered from the cut‐off damage exhibited the tensile strength of 41.5 MPa and the elongation at break of 940%. On the contrary, MPE modified CWPU exhibited remarkable reinforcement effect on the CWPU films, and the tensile strength reached ~50 MPa but with the sacrificed reversibility. The enhanced thermal stability and surface hydrophobicity were also pronounced on the MPE modified CWPU. The very different roles of the Hou Po‐bisphenols are in sharply distinctive from their petrochemical analogs, providing new insights into the design of biologically sourced materials.

RAFT-mediated polymerization-induced self-assembly (RAFT-PISA) has been fast developed nowadays, promoting the research toward more diverse morphologies and more cutting-edge applications. Here, we demonstrate a polymerization-pH tailored RAFT-PISA (pH-PISA) process, which can conveniently harvest abundant nano/micro-scale morphologies using the popular monomers of N,N-dimethylacrylamide (DMAA) and diacetone acrylamide (DAAM). The process proceeded through ordinary RAFT dispersion polymerization in the aqueous medium but at different pH conditions. With the use of the pH-sensitive bi-carboxylic acid-capped trithiocarbonate as the chain transfer agent (CTA), it has been found that the PISA of the propagating amphiphilic ABA triblock copolymers was highly affected by the different ionization of the CTA. When the polymerization pH was adjusted to 2.5, an especially wide spectrum of morphologies was detected including the spheres, worms, lamellae, single or double-head tadpoles, vesicle strings and large spheres with surface protrusions. However, the morphology diversity gradually declined when the polymerization pH was increased to 6 or 8. The diverse structures with the same monomer compositions provide an ideal model to explore the influence of particle morphology on ice recrystallization inhibition (IRI) activities. The variations on both the mean largest grain sizes (MLGS) and growth rates of the single ice crystal were related to the packing parameters (P), bridging the interface geometry of the packing of the amphiphilic molecules and ice-controlling activities.

Herein, we describe a one-step method for synthesizing cationic acrylate-based core-shell latex (CACS latex), which is used to prepare architectural coatings with excellent antimicrobial properties. Firstly, a polymerizable water-soluble quaternary ammonium salt (QAS-BN) was synthesized using 2-(Dimethylamine) ethyl methacrylate (DMAEMA) and benzyl bromide by the Hoffman alkylation reaction. Then QAS-BN, butyl acrylate (BA), methyl methacrylate (MMA), and vinyltriethoxysilane (VTES) as reactants and 2,2’-azobis(2-methylpropionamidine) dihydrochloride (AIBA) as a water-soluble initiator were used to synthesize the CACS latex. The effect of the QAS-BN dosage on the properties of the emulsion and latex film was systematically investigated. The TGA results showed that using QAS-BN reduced the latex film’s initial degradation temperature but improved its thermal stability. In the transmission electron microscopy (TEM) photographs, the self-stratification of latex particles with a high dosage of QAS-BN was observed, forming a core-shell structure of latex particles. The DSC, TGA, XPS, SEM, and performance tests confirmed the core-shell structure of the latex particles. The relationship between the formation of the core-shell structure and the content of QAS-BN was proved. The formation of the core-shell structure was due to the preferential reaction of water-soluble monomers in the aqueous phase, which led to the aggregation of hydrophilic groups, resulting in the formation of soft-core and hard-shell latex particles. However, the water resistance of the films formed by CACS latex was greatly reduced. We introduced a p-chloromethyl styrene and n-hexane diamine (p-CMS/EDA) crosslinking system, effectively improving the water resistance in this study. Finally, the antimicrobial coating was prepared with a CACS emulsion of 7 wt.% QAS-BN and 2 wt.% p-CMS/EDA. The antibacterial activity rates of this antimicrobial coating against E. coli and S. aureus were 99.99%. The antiviral activity rates against H₃N₂, HCoV-229E, and EV71 were 99.4%, 99.2%, and 97.9%, respectively. This study provides a novel idea for the morphological design of latex particles. A new architectural coating with broad-spectrum antimicrobial properties was obtained, which has important public health and safety applications.

The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to para-aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites.

Polymer solar cells (PSCs) typically suffer from a negative effect of the residual solvent on the performance due to the use of the solvent processing additive. One solution to solve this problem is to use a solid polymer additive that can promote the phase separation of the blend film of the active layers. In this work, two new D−A type photovoltaic polymers, namely PIT‐DTBT and PIT‐DTffBT, based on asymmetric indenothiophene (IT) donor unit and nonfluorinated or difluorinated benzothiadiazole acceptor unit were designed and synthesized, respectively. Then a triblock copolymer, poly(styrene‐ block ‐butadiene‐ block ‐styrene) (SBS), was employed as a polymer additive into the active layers of PIT‐DTBT/PC ₇₁ BM and PIT‐DTffBT/PC ₇₁ BM based devices, and the SBS effect on the morphology of the blend films of the active layers, and then the performance of the two kinds of devices was investigated. The results demonstrated that the addition of SBS improved the molecule packing and induced the crystallization of PIT‐DTffBT, making the device have higher charge mobilities, more efficient charge dissociation and collection, and less charge recombination. Thus, power conversion efficiency (PCE) was increased from 4.61 % to 6.57 % for PIT‐DTffBT based device. Although almost no improvement in molecule packing and crystallization was observed for SBS‐treated nonfluorinated PIT‐DTBT, the fact of PCE of the PIT‐DTBT based device increased from 2.94 % to 3.13 % can also be attributed to the improved phase separation of the blend film by SBS. These findings indicate that SBS is more sensitive to fluorinated polymers than nonfluorinated polymers in improving molecule packing and inducing crystallization.

In order to improve adhesion properties of waterborne polyurethane (WPU) inks on biaxially oriented polypropylene (BOPP) films, herein, a liquid polyester polyol BY3003 with long‐branched aliphatic chains was used to prepare WPU latexes suitable for BOPP films printing. The application of BY3003 made the surface tension of the prepared latexes not more than 43 mN/m, while that of traditional WPU latex exceeded 55 mN/m. Accordingly, the T‐peel strength of the inks made from these latexes was all above 0.8 N/15 mm. In addition, post chain extension degree, dimethylol butyric acid content, and NCO/OH molar ratio also had significantly effect on latex and film properties of WPU, especially on the T‐peel strength of the corresponding inks. By optimizing these factors, a WPU latex with surface tension as low as 39.6 mN/m and adhesion fastness over 95% on BOPP film were obtained, and the T‐peel strength of its corresponding ink was up to 2.05 N/15 mm, which is the highest value recorded in the literature as far as we know.