Julolidine-labelled fluorinated block copolymers for the development of two-layer films with highly sensitive vapochromic response

Molecular Rotors with Aggregation-Induced Emission (AIE) as Fluorescent Probes for the Control of Polyurethane Synthesis

In this work, the use of fluorescent molecular rotors such as 9-(2,2-dicyanovinyl)julolidine (DCVJ) and 2,3-bis(4-(phenyl(4-(1,2,2-triphenylvinyl) phenyl)amino)phenyl)fumaronitrile (TPETPAFN) was proposed for the real-time monitoring of polyurethane (PU) formation in a solution of dimethylacetamide starting with 4,4′-methylenediphenyl diisocyanate (MDI) and different polyethylene glycols (PEG400 and PEG600) as diols. Notably, relative viscosity variations were compared with fluorescence changes, recorded as a function of the polymerization progress. The agreement between these two parameters suggested the innovative use of a low-cost fluorescence detection system based on a LED/photodiode assembly directly mountable on the reaction apparatus. The general validity of the proposed experiments enabled the monitoring of polyurethane polymerization and suggested its effective applications to a variety of industrial polymers, showing viscosity enhancement during polymerization.

The Effect of Poly(ethylene glycol) (PEG) Length on the Wettability and Surface Chemistry of PEG-Fluoroalkyl-Modified Polystyrene Diblock Copolymers and Their Two-Layer Films with Elastomer Matrix

Diblock copolymers composed of a polystyrene first block and a PEG-fluoroalkyl chain-modified polystyrene second block were synthesized by controlled atom transfer radical polymerization (ATRP), starting from the same polystyrene macroinitiator. The wettability of the polymer film surfaces was investigated by measurements of static and dynamic contact angles. An increase in advancing water contact angle was evident for all the films after immersion in water for short times (10 and 1000 s), consistent with an unusual contraphilic switch of the PEG-fluoroalkyl side chains. Such a contraphilic response also accounted for the retained wettability of the polymer films upon prolonged contact with water, without an anticipated increase in the hydrophilic character. The copolymers were then used as surface-active modifiers of elastomer poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS)-based two-layer films. The elastomeric behavior of the films was varied by using SEBS matrices with different amounts of polystyrene. Whereas the mechanical properties strictly resembled those of the nature of the SEBS matrix, the surface properties were imposed by the additive. The contraphilic switch of the PEG-fluoroalkyl side chains resulted in an exceptionally high enrichment in fluorine of the film surface after immersion in water for seven days.

Fluorinated vs. Zwitterionic-Polymer Grafted Surfaces for Adhesion Prevention of the Fungal Pathogen Candida albicans

Fluorinated (F6) and zwitterionic, as well as phosphorylcholine (MPC) and sulfobetaine (MSA), copolymers containing a low amount (1 and 5 mol%) of 3-(trimethoxysilyl)propyl methacrylate (PTMSi) were prepared and covalently grafted to glass slides by using the trimethoxysilyl groups as anchorage points. Glass-surface functionalization and polymer-film stability upon immersion in water were proven by contact angle and angle-resolved X-ray photoelectron spectroscopy (AR-XPS) measurements. Antifouling performance of the grafted films was assayed against the yeast Candida albicans, the most common Candida species, which causes over 80% of candidiasis. Results revealed that the F6 fluorinated, hydrophobic copolymers performed much better in reducing the adhesion of C. albicans, with respect to both corresponding zwitterionic, hydrophilic MPC and MSA counterparts, and were similar to the glass negative control, which is well-known to inhibit the adhesion of C. albicans. A composition-dependent activity was also found, with the films of copolymer with 99 mol% F6 fluorinated co-units performing best.

Mechanochromic Fluorescent Polymers with Aggregation-Induced Emission Features

Mechanochromic polymers are defined as materials that are able to detect a mechanical stress through an optical output. This feature has evoked a growing interest in the last decades, thanks to the progress of chromogenic molecules whose optical characteristics and chemical functionalities allow their effective insertion in many thermoplastic and thermoset matrices. Among the different types of fluorogenic probes able to detect mechanical solicitations, those with aggregation-induced emission (i.e., AIEgens) have attracted tremendous interest since their discovery in 2001. In the present review, the main principles behind the AIEgens working behavior are introduced along with the current state of knowledge concerning the design and preparation of the derived mechanochromic fluorescent polymers. Examples are provided concerning the most ingenious solution for the preparation of chromogenic materials, starting from different types of commodity plastics or synthetic polymers and combined with the latest AIE technology to provide the most sensitive response to mechanical stress.

Surface Segregation of Amphiphilic PDMS-Based Films Containing Terpolymers with Siloxane, Fluorinated and Ethoxylated Side Chains

(Meth)acrylic terpolymers carrying siloxane (Si), fluoroalkyl (F) and ethoxylated (EG) side chains were synthesized with comparable molar compositions and different lengths of the Si and EG side chains, while the length of the fluorinated side chain was kept constant. Such terpolymers were used as surface-active modifiers of polydimethylsiloxane (PDMS)-based films with a loading of 4 wt%. The surface chemical compositions of both the films and the pristine terpolymers were determined by angle-resolved X-ray photoelectron spectroscopy (AR-XPS) at different photoemission angles. The terpolymer was effectively segregated to the polymer−air interface of the films independent of the length of the constituent side chains. However, the specific details of the film surface modification depended upon the chemical structure of the terpolymer itself. The exceptionally high enrichment in F chains at the surface caused the accumulation of EG chains at the surface as well. The response of the films to the water environment was also proven to strictly depend on the type of terpolymer contained. While terpolymers with shorter EG chains appeared not to be affected by immersion in water for seven days, those containing longer EG chains underwent a massive surface reconstruction.