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Poly(methyl methacrylate-b-styrene) (PMMA-b-PS) block copolymers are synthesized by two consecutive ATRPs and fractionated into four fractions. The halogen chain end fidelity (CEF) in PMMA-b-PS is quantified based on the analysis of each fraction. Compared to ethyl 2-phenyl-2-bromoacetate/CuBr/2,2′-bipyridine (EPBA/CuBr/bpy) and CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine (CuBr/PMDETA) catalysts, PMMA-b-PS synthesized using p-toluenesulfonyl chloride/CuCl/bpy (TsCl/CuCl/bpy) and CuCl/PMDETA catalysts has a higher halogen CEF and a better control on molecular weight. [ABSTRACT FROM AUTHOR]

The molecular transfer printing (MTP) technique has been invented to fabricate chemical patterns with high fidelity using homopolymer inks. In this work, we systematically studied the effects of the molecular weights of homopolymer inks and transfer conditions on the MTP process. We explored a large range of molecular weights (∼3.5−56 kg·mol−1) of hydroxyl-terminated polystyrene (PS-OH) and hydroxyl-terminated poly(methyl methacrylate) (PMMA-OH) in the MTP process, and found that the resulting chemical patterns on replicas from all five blends were functional and able to direct the assembly of films of the same blends. The transfer temperature and the film annealing sequences had an impact on the MTP process. MTP was sensitive to the transfer temperature and could only be performed within a certain temperature range, i.e. higher than the glass transition temperature (Tg) of copolymers and lower than the rearrangement temperature of the assembled domains. Pre-organization of the blend films was also necessary for MTP since the preferential wetting of PMMA domains at the replica surface might result in the formation of a PMMA wetting layer to prevent the presentation of underlying chemical patterns to the replica surface. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs) have been considered as an alternative to small molecule antibiotics since they are difficult to develop antimicrobial resistance. Hyperbranched polylysine (HPL), an AMP mimics, has gained attention due to its broad-spectrum antibacterial activities, but it also suffers from high toxicity. Here we report a facile strategy to engineer the toxicity of HPL by copolymerizing lysine (K) with a hydrophobic amino acid, e.g., alanine (A), tryptophan (W) or phenylalanine (F), to afford hyperbranched random copolymers. These copolymers have comparable antibacterial activities to HPL while their cytotoxicities and in vivo toxicities are lowered when the type and content of hydrophobic amino acid and the size of copolymers are optimized. The G. mellonella infection model demonstrates that the copolymers are effective against the S. aureus infection in vivo. The copolymers kill the bacteria through the disruption of cell membranes and the bacteria do not develop resistance to the copolymers. [ABSTRACT FROM AUTHOR]

Block copolymer lithography is emerging as one of the leading technologies for patterning nanoscale dense features. In almost all potential applications of this technology, control over the orientation of cylindrical and lamellar domains is required for pattern transfer from the block copolymer film. This review highlights the state-of-art development of brushes to modify the substrates to control the assembly behaviors of block copolymers in films. Selected important contributions to the development of self-assembled monolayers, polymer brushes and mats, and chemically patterned brushes are discussed. [ABSTRACT FROM AUTHOR]

Medical devices-related infections pose a great threat to patients and cause an increased morbidity and mortality. Herein, we prepare an antibacterial composite (TPU-x) through blending medical grade thermoplastic polyurethane (TPU) and the complex (PL-DOSS) of ε-polylysine (ε-PL) and docusate sodium (DOSS). >99% reduction of colony forming unit (CFU) can be obtained in TPU-x composite films even at relatively low content of PL-DOSS, e.g. 0.13% for Methicillin resistant S. aureus (MRSA) and 0.5% for E. coli. The excellent antibacterial activity is mainly attributed to the formation of PL-DOSS nanoparticles that are uniformly dispersed in the TPU matrix with a size of ∼100 nm. TPU-x composite films exhibit long-term stability in saline and good biocompatibility, and retain mechanical properties of TPU. [ABSTRACT FROM AUTHOR]

Data concerning the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in asymptomatic and paucisymptomatic patients are lacking. We report a 3-family cluster of infections involving asymptomatic and paucisymptomatic transmission. Eight of 15 (53%) members from 3 families were confirmed with SARS-CoV-2 infection. Of 8 patients, 3 were asymptomatic and 1 was paucisymptomatic. An asymptomatic mother transmitted the virus to her son, and a paucisymptomatic father transmitted the virus to his 3-month-old daughter. SARS-CoV-2 was detected in the environment of 1 household. The complete genomes of SARS-CoV-2 from the patients were > 99.9% identical and were clustered with other SARS-CoV-2 sequences reported from China and other countries. [ABSTRACT FROM AUTHOR]