In the present work, crystallization-driven coassembly of micrometric polymer single crystals and nanometric block copolymer micelles was achieved. The hybrid single crystals are first formed by cocrystallization of polyethylene (PE) homopolymer and polyethylene-b-poly(tert-butyl acrylate) (PE-b-PtBA) block copolymer (BCP) in DMF or DMF/o-xylene mixed solvent. The morphology of the obtained hybrid single crystals can be regulated via changing the solvent composition, crystallization temperature and mass ratio of BCP/homopolymer. Because of the difference in crystallization rate, the distribution of PE-b-PtBA BCP in the hybrid single crystals may be inhomogeneous, leading to a concave gradient surface structure. The hybrid single crystals have a double-layer structure, in which PE homopolymer chains adopt extended conformation and the PE blocks in PE-b-PtBA are probably once-folded. After the PE homopolymer is consumed, cylindrical micelles of PE-b-PtBA can further epitaxially grow on the lateral surface of the hybrid single crystals and "ciliate paramecium-like" coassemblies are yielded. The single crystal/micelles coassemblies can be prepared either by one-step method, in which PE and PE-b-PtBA are added together in a single step, or by two-step method, in which the hybrid single crystals are prepared in the first step and extra PE-b-PtBA is added in the second step to grow BCP micelles. This work provided a simple route to construct hierarchical assemblies composed of objects with different scales by using crystallization as the key driving force.
A semicrystalline poly(trimethylene monothiocarbonate) (PTMMTC) has been synthesized via the selective and alternating copolymerization of carbonyl sulfide and oxetane. This reaction was catalyzed by (salen)CrCl accompanied by organic bases over a wide range of temperatures from 40 to 130 °C. PTMMTC is shown to exhibit similar crystallization behavior to high-density polyethylene (HDPE), i.e., being spherulite and possessing melting temperatures (T m ) up to 127.5 °C and a degree of crystallinity (X c ) of up to 71%. Moreover, PTMMTC has a wide processing temperature window of ca. 100 °C.
Lower disorder-to-order transition (LDOT) phase behavior is seldom observed in block copolymers (BCPs). Design of LDOT BCPs is important for broadening the applications and improving the high temperature properties of BCPs. In this work, the LDOT phase behavior was first achieved in the strongly interacting BCPs consisting of poly(ethylene oxide) (PEO) and poly(ionic liquid) (PIL) blocks (EO m -b-(IL-X) n , X: counterion) by introducing two extra strong forces (hydrogen-bonding and Coulombic interaction) with different temperature dependences. It is also found that the LDOT phase behavior of the EO m -b-(IL-X) n BCPs can be regulated by molecular weight (related to mixing entropy), counterion, and salt doping. Increasing counterion size and salt content shifts the disorder-to-order transition temperature (T DOT ) to higher temperature, whereas a higher molecular weight leads to a lower T DOT . Based on our findings, some general rules for design of LDOT phase behavior in the strongly interacting BCPs were proposed. Moreover, the conductivity of the EO m -b-(IL-X) n BCPs was correlated with the LDOT phase behavior. A remarkable increase in conductivity after LDOT, i.e., a thermo-activated transition, is observed for the EO m -b-(IL-X) n BCPs, which can be attributed to the cooperative effects of temperature rising and LDOT.
The genomes of coronaviruses carry accessory genes known to be associated with viral virulence. The single accessory gene of porcine epidemic diarrhea virus (PEDV), ORF3, is dispensable for virus replication in vitro, while viral mutants carrying ORF3 truncations exhibit an attenuated phenotype of which the underlying mechanism is unknown. Here, we studied the effect of ORF3 deletion on the proliferation of PEDV in Vero cells. To this end, four recombinant porcine epidemic diarrhea viruses (PEDVs) were rescued using targeted RNA recombination, three carrying the full-length ORF3 gene from different PEDV strains, and one from which the ORF3 gene had been deleted entirely. Our results showed that PEDVs with intact or naturally truncated ORF3 replicated to significantly higher titers than PEDV without an ORF3. Further characterization revealed that the extent of apoptosis induced by PEDV infection was significantly lower with the viruses carrying an intact or C-terminally truncated ORF3 than with the virus lacking ORF3, indicating that the ORF3 protein as well as its truncated form interfered with the apoptosis process. Collectively, we conclude that PEDV ORF3 protein promotes virus proliferation by inhibiting cell apoptosis caused by virus infection. Our findings provide important insight into the role of ORF3 protein in the pathogenicity of PEDV.
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