One-Pot Synthesis of Branched Poly(styrene−divinylbenzene) Suspension Polymerized Resins

Cleavable Comonomers for Chemically Recyclable Polystyrene: A General Approach to Vinyl Polymer Circularity

Many common polymers, especially vinyl polymers, are inherently difficult to chemically recycle and are environmentally persistent. The introduction of low levels of cleavable comonomer additives into existing vinyl polymerization processes could facilitate the production of chemically deconstructable and recyclable variants with otherwise equivalent properties. Here, we report thionolactones that serve as cleavable comonomer additives for the chemical deconstruction and recycling of vinyl polymers prepared through free radical polymerization, using polystyrene (PS) as a model example. Deconstructable PS of different molar masses (∼20-300 kDa) bearing varied amounts of statistically incorporated thioester backbone linkages (2.5-55 mol %) can be selectively depolymerized to yield well-defined thiol-terminated fragments (<10 kDa) that are suitable for oxidative repolymerization to generate recycled PS of nearly identical molar mass to the parent material, in good yields (80-95%). A theoretical model is provided to generalize this molar mass memory effect. Notably, the thermomechanical properties of deconstructable PS bearing 2.5 mol % of cleavable linkages and its recycled product are similar to those of virgin PS. The additives were also shown to be effective for deconstruction of a cross-linked styrenic copolymer and deconstruction and repolymerization of a polyacrylate, suggesting that cleavable comonomers may offer a general approach toward circularity of many vinyl (co)polymers.

Phenylglyoxaldehyde-Functionalized Polymeric Sorbents for Urea Removal from Aqueous Solutions

For realization of a wearable artificial kidney based on regeneration of a small volume of dialysate, efficient urea removal from dialysate is a major challenge. Here a potentially suitable polymeric sorbent based on phenylglyoxaldehyde (PGA), able to covalently bind urea under physiological conditions, is described. Sorbent beads containing PGA groups were obtained by suspension polymerization of either styrene or vinylphenylethan-1-one (VPE), followed by modification of the aromatic groups of poly(styrene) and poly(VPE) into PGA. It was found that PGA-functionalized sorbent beads had maximum urea binding capacities of 1.4-2.2 mmol/g and removed ∼0.6 mmol urea/g in 8 h at 37 °C under static conditions from urea-enriched phosphate-buffered saline, conditions representative of dialysate regeneration. This means that the daily urea production of a dialysis patient can be removed with a few hundred grams of this sorbent which, is an important step forward in the development of a wearable artificial kidney.

Effect of poly(acrylic acid) architecture on setting and mechanical properties of glass ionomer cements

OBJECTIVE

This work focuses on the influence of poly(acrylic acid) (PAA) architecture (linear or branched) on setting behavior and compressive strength of glass ionomer cements (GICs).

METHODS

Branched and linear poly(acrylic acid)s were synthesized according to the Strathclyde methodology or by free radical polymerization. They were characterized by ¹H-NMR spectroscopy and size exclusion chromatography to determine their molecular weight and size distribution. GIC setting was characterized by oscillating rheometry and time-dependent FTIR spectroscopy. In addition, compressive strength was tested on cylindrical samples (6 × 4 mm; n = 8/cement composition) after storage in deionized water at 37 °C for one day.

RESULTS

We used two different routes to prepare PAA. One direct route in order to provide straightforward access to branched PAA and a two-step approach in order to get more control about the PAA molecular weight using tert-butyl acrylate (tBA) for polymerization with subsequent deprotection. Using the second approach we obtained several linear PAA of which a mixture was used in order to mimic the molecular weight and size distribution of branched PAA. This allowed the direct comparison of properties relying only on the polymer architecture. Comparing linear PAA to branched samples in general led to faster setting but at the same time decreased the compressive strength. Increasing molecular weight of branched PAA resulted in even faster GIC setting while increasing compressive strength and this correlates well with the trends reported for linear PAA in literature. Mixing of branched and linear PAA, however, turned out to be an effective way of tailoring GIC properties.

SIGNIFICANCE

our results suggest that both molecular weight and dispersity need to be considered when choosing suitable PAA architecture for obtaining specific GIC properties.

Techno-Economic Analysis of Glycerol Valorization via Catalytic Applications of Sulphonic Acid-Functionalized Copolymer Beads

The design of experiments response surface analysis was employed for the first time to study the effect of divinylbenzene (DVB) (20-80 wt. %), diluent (0-100 wt.%), and mixing (200-900 rpm) on the beads' physical properties and on swelling ability. The beads with the highest performances, in terms of mechanical stability, surface area, and swelling ability, were sulphated, and tested in converting glycerol to a valuable product "solketal." Process options for glycerol valorization to solketal using synthesized sulphonic acid-functionalized styrene-divinylbenzene (ST-DVB-SO3H) copolymer beads and techno-economic analysis of the processes have been investigated. Three processes were evaluated: two one-stage processes at 8.5 wt.% catalyst and 50°C, based on either 6:1 acetone to glycerol molar ratio (87% conversion) or 12:1 (98% glycerol to solketal conversion), and a two-stage route (two acetone additions), where ≥98% conversion can be achieved with lower overall acetone use (10:1 acetone to glycerol molar ratio and 50°C). Techno-economic analyses of the three solketal options were performed using Aspen (HYSYS), based on a fixed capacity of 100,000 te/y and 20-years lifetime. The techno-economic analyses showed that the net present values for the solketal process options were $707 M for the two-stage, $384 M for the one-stage at 6:1 acetone to glycerol molar ratio, and $703 M for the one-stage at 12:1 acetone to glycerol molar ratio. The break-even prices for these solketal processes were $2,058/ ton for the one-stage at 12:1 of acetone and two-stage and $2,088/ton for the one-stage at 6:1 of acetone, which is lower than the current price of solketal at $3,000/ton. The two-stage process was found to be the most effective method of glycerol valorization production to solketal.

Investigation on Adsorption Mechanism of Peptides with Surface-Modified Super-Macroporous Resins

Macroporous adsorption resins (MARs) have experienced rapid growth because of their unique properties and applications. Recently, it was discovered that a series of MARs with super-macroporous and diverse functional groups were synthesized to adsorb and enrich peptides; however, the detailed change mechanism of pore diameter and element composition and peptide adsorption mechanism have not yet been established. In this study, MARs and modified MARs were prepared by the surfactant reverse micelles swelling method and Friedel-Crafts reaction, and the pore diameter and element changes of these super-macroporous resin particles were accurately determined to elucidate formation processes of modified MARs. The adsorption mechanism of four peptides on different MARs was investigated. Sieving effect, electrostatic, hydrophobic, and hydrogen bonds interactions were found to play a major role in the adsorption process of peptides. Compared to that of the traditional resins, the adsorption capacity of super-macroporous MARs for peptides enormously increased. Electrostatic interactions have been explained perfectly by determining the isoelectric point. The molecular docking technology proved that the hydrogen-bonding receptor in MARs was a crucial factor for the adsorption capacity by autodock 4.26 and gromacs 5.14. These findings will enable selective adsorption of peptides by MARs, which also provides a theoretical basis for the construction of specific resin to adsorb different peptides.

Synthesis and degradation of branched, photo-labile poly(acrylic acid) and polystyrene

We present the synthesis, characterization and photolytical degradation of branched photo-responsive poly(acrylic acid) and polystyrene using free radical polymerization of acrylic acid/styrene in the presence of a newly synthesized asymmetric o-nitrobenzyl-based crosslinker and different amounts of dodecanethiol (DDT) as a chain transfer agent.

Facile photo-flow synthesis of branched poly(butyl acrylate)s

We present the synthesis of branched poly(butyl acrylate)s using photo-induced free radical polymerization of (n/t)-butyl acrylate in the presence of tri(propylene glycol) diacrylate (TPGDA) as a crosslinker and varying amounts of dodecanethiol (DDT) as a chain transfer agent to prevent macroscopic gelation.

Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields.

Polymerization Initiated by Particle Contact: A Quiescent State Trigger for Materials Synthesis

Dispersions of particles onto which reactive groups are bound give rise to inhomogeneous concentrations that may afford fundamentally different chemical behavior compared to the same molecular species dissolved in homogeneous solution. An example is bimolecular reactivity of complementary-functionalized particles, whereby interparticle contact is expected to promote fast kinetics localized to the interface, while exhibiting essentially no reactivity elsewhere. Such materials may exhibit unique properties analogous to blood clotting and thereby be useful in self-healing applications. Here, we demonstrate a radical polymerization reaction whose initiation is controlled by the physical proximity of two complementary co-initiators bound to a substrate and/or polymer beads. Polymerization of the surrounding acrylate monomer only occurs when interfaces functionalized with dimethylaniline encounter interfaces bearing benzoyl peroxide. At the interface of the complementary-functionalized beads, polymerization affords a "clot-like" scaffold of beads and polymer. Interestingly, such a scaffold is only attained when the beads are in a quiescent state. These findings open the way to the design of spatially controlled dual initiator systems and novel self-healing strategies and motifs.

Methanolysis of organophosphorus esters promoted by an M2+ catalyst supported on polystyrene-based copolymers

The methanolysis of three neutral organophosphorus esters (a phosphonate, a phosphonothioate, and a phosphorothionate) promoted by several polymer-supported Zn(II) or Cu(II) containing catalysts was studied. The catalysts consist of a Zn(II) or Cu(II) complex with 1,5,9-triazacyclododecane or phenanthroline attached to a porous polystyrene resin. In each case, the polymer supported catalyst showed activity at near neutral sspH in methanol (8.38) and ambient temperature and provided accelerations of up to a factor of 2.9 × 106 relative to the background reaction at sspH 9.05. The solid materials could be reused several times and could be reactivated when the activity diminished. Various polymers of different porosity and extent of cross-linking were studied, with the net result being that larger porosities offer the best reactivity for catalyzed methanolysis of these OP species in methanol. This is explained by different parameters including the accessibility to reactive sites, the increase of concentration of catalytic sites on the surface of the polymer, and some cooperative effects between neighboring catalytic groups.Key words: functionalized polymer, metal containing, methanolysis, organophosphorus pesticides and CW agents, catalyst.

Soft shell resins for solid-phase peptide synthesis

Soft shell (SS) resins with a lightly or noncross-linked shell layer were prepared by reducing the amount of cross-linking agent, divinylbenzene (DVB), during seed suspension polymerization from polystyrene (PS) resin. These SS resins have a lower swelling volume than that produced by normal cross-linking. Despite its lower swelling, however, SS (10-00) resin, which consists of the 1% DVB-cross-linked core and the noncross-linked surface layer, showed higher efficiency in peptide synthesis compared with 1% DVB-PS resin and other SS resins.