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PEG is the gold standard polymer for pharmaceutical applications, however it lacks degradability. Degradation under physiologically relevant pH as present in endolysosomes, cancerous and inflammatory tissues is crucial for many areas. The authors present anionic ring‐opening copolymerization of ethylene oxide with 3,4‐epoxy‐1‐butene (EPB) and subsequent modification to introduce acid‐degradable vinyl ether groups as well as methacrylate (MA) units, enabling radical cross‐linking. Copolymers with different molar ratios of EPB, molecular weights (Mn) up to 10 000 g mol−1 and narrow dispersities (Đ<1.05) were prepared. Both the P(EG‐co‐isoEPB)MA copolymer and the hydrogels showed pH‐dependent, rapid hydrolysis at pH 5–6 and long‐term storage stability at neutral pH (pH 7.4). By designing the degree of polymerization and content of degradable vinyl ether groups, the release time of an entrapped protein OVA‐Alexa488 can be tailored from a few hours to several days (hydrolysis half‐life time t1/2 at pH 5: 13 h to 51 h). [ABSTRACT FROM AUTHOR]

In contrast to acetal groups, aminal moieties are almost unknown in polymer chemistry. The aminal-protected isopropyl-hexahydro-pyrimidine glycidyl amine (PyGA) for the anionic ring-opening polymerization (AROP) is introduced. The monomer is prepared in a two-step synthesis and can be polymerized in a well-controlled manner under AROP conditions. Several poly(ethylene glycol) block and triblock copolymers are synthesized in a molecular weight range from 2 700 to 11 400 g mol-1 with up to 11 mol% PyGA. The molecular weight distributions are monomodal with low dispersity (Đ = Mw/Mn) below 1.2. After the polymerization, the acid-labile hexahydropyrimidine rings can be conveniently cleaved in acidic media, liberating two secondary amines per PyGA monomer unit. The released 1,3-diamine functionalities can be addressed via post-polymerization modification and show complexation of copper(II) ions in aqueous solution. The compounds are promising for water-soluble catalyst systems, the removal of transition metals from water, and as a building block for complexing polyethers for biomedical application. [ABSTRACT FROM AUTHOR]

Abstract: Eine ideale, statistische anionische Copolymerisation wird durch physikalische Trennung der beiden Monomere in Kompartimente einer Emulsion gezwungen, um so Gradientencopolymere zu bilden. Das eine Monomer (M) ist vorzugsweise in den Tröpfchen löslich, während das andere (D) die kontinuierliche Phase einer DMSO‐in‐Cyclohexan‐Emulsion bevorzugt. Die lebende anionische Copolymerisation von zwei aktivierten Aziridinen ist auf die DMSO‐Kompartimente beschränkt, da die Polymerisation selektiv in diesen Tröpfchen stattfindet. Über die Verdünnung der kontinuierlichen Phase wird die lokale Konzentration von Monomer D in den Tröpfchen bestimmt und folglich der Gradient des resultierenden Copolymers. Die Copolymerisationen in der Emulsion werden durch Echtzeit‐1H‐NMR‐Kinetiken überwacht, was die Änderung der Copolymerisationsparameter beider Monomere bei Verdünnung der kontinuierlichen Phase von ideal statistischen Copolymeren zu Gradientencopolymeren zeigt. [ABSTRACT FROM AUTHOR]

Abstract: An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO‐in‐cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real‐time 1H NMR kinetics, proving a change of the reactivity ratios of the two monomers upon dilution of the continuous phase from ideal random to adjustable gradients by simple dilution. [ABSTRACT FROM AUTHOR]

Multi-amino-functional poly(propylene oxide) (PPO) copolymers were synthesized by the anionic ring-opening copolymerization (AROP) of N, N-diethyl glycidyl amine (DEGA) and propylene oxide (PO). A solvent free synthesis route using potassium counterions and crown ether for the AROP enabled controlled (co)polymerization with full conversion. The strategy provided access to PPO-b-PDEGA block copolymers, statistical PPO-co-PDEGA copolymers, and, for the first time, PDEGA homopolymer. Molecular weights in the range of 1400 to 4200 g/mol (Mn) and dispersities (Mw/Mn) below 1.1 were obtained. Both the kinetics and resulting microstructure of the statistical copolymerization were investigated by in situ 1H NMR spectroscopy, revealing reactivity ratios of rPO = 1.7 and rDEGA = 0.9. The polyethers exhibit thermoresponsive behavior in aqueous solution, showing cloud points in the range 14-57 °C under neutral conditions. Because of the amine groups, the copolymer structures are strongly affected by the pH of the solution, and therefore the cloud points are highly pH-dependent. By changing the pH of the polymer solution, the cloud points can be tuned between 5 and 100 °C, as studied by turbidity measurements. The copolymers offer new potential for PPO-based structures for surface modification, biomedical purposes and pharmaceutical application. [ABSTRACT FROM AUTHOR]

N‐Heterocyclic olefin (NHO)‐based polymerization pathways for the copolymerization of ethylene oxide (EO) and propylene oxide (PO) are investigated in detail. Employing in situ 1H NMR spectroscopy, both an organocatalytic, anionic polymerization setup (system A) and a zwitterionic, Lewis pair‐type approach (system B) are studied comparatively. The obtained kinetics data are fitted to the non‐terminal model (Jaacks and Ideal Integrated) and terminal Mayo–Lewis model (Meyer Lowry) to determine the reactivity ratios, revealing striking differences in copolyether microstructure and achievable molar masses. While for the metal‐free catalysis (system A) reactivity ratios of rEO = 3.4 and rPO = 0.30 are found, indicating a soft gradient structure, the presence of Mg(HMDS)2 (system B) entails exclusively zwitterionic propagation. This results in enhanced selectivity, displaying corresponding parameters of rEO = 7.9 and rPO = 0.13, in line with the proposed monomer‐activated mechanism. The block‐like, strongly tapered copolyether microstructure is also reflected in the thermal properties, showing a melting point for the latter sample and much higher molar masses (Mn >50 000 g mol−1). Notably, this study not only identifies capable polymerization systems for EO/PO, but also underlines that via in situ 1H NMR kinetics key questions regarding the polymerization mechanism can be illuminated quickly and reliably, simplifying access to essential structure‐property relations. [ABSTRACT FROM AUTHOR]

The copolymerization of glycidyl cinnamate (GC) as a hitherto non‐polymerizable, photoreactive epoxide structure to aliphatic polyether copolymers is described, using the monomer‐activated epoxide ring‐opening polymerization (MAROP). Ethoxyethyl glycidyl ether (EEGE) and GC are copolymerized employing triisobutylaluminum (i‐Bu3Al) as a catalyst and tetraoctylammonium bromide (NOctBr4) as an initiator. The amount of GC varies from 3 mol% to 100 mol%, which results in apparent molecular weights in the range of 2600 to 4600 g mol−1 and dispersities (Đ) below 1.34. Studies of the microstructure by in‐situ 1H NMR kinetics indicate a gradient‐like distribution of EEGE and GC (reactivity ratios: rEEGE = 0.28; rGC = 3.6), applying the ideal copolymerization model for evaluation. A tentative explanation relies on differing bond lengths in the respective epoxide rings, as suggested by density functional theory (DFT) calculations. Mild and selective cleavage of the acetal protecting groups of EEGE is achieved using the acidic ionic resin Dowex, leaving the GC ester bonds intact (Mn = 1900–3700 g mol−1, Đ < 1.34). Thermal properties of the copolymers and the PGC homopolymer are investigated by differential scanning calorimetry (DSC). The crosslinking of P(G‐co‐GC) copolymers by UV irradiation allows hydrogel formation, which is confirmed by IR spectroscopy. [ABSTRACT FROM AUTHOR]

The anionic ring opening polymerizations of ethylene oxide (EO) and propylene oxide (PO) are performed by using 1,3,5‐triethanol hexahydro‐1,3,5‐triazine (TrAz) as a "sacrificial" trifunctional initiator. Well‐defined three‐arm star polymers are obtained with a narrow molecular weight distribution (Mw/Mn < 1.1). Molecular weights range from 3–15 kg mol−1. Since these star polymers possess an acid‐labile hexahydro‐triazine core, acidic hydrolysis leads to cleavage of the arms. This gives access to well‐defined α‐amino‐ω‐hydroxyl heterobifunctional poly(ethylene glycol) (PEG) and poly(propylene oxide) (PPO) in the molecular weight range of 1–5 kg mol−1 and low dispersity Mw/Mn < 1.1. The α,ω‐heterobifunctional polyethers are valuable structures for bioconjugation. Furthermore, an acid‐labile triazine star polymer is directly used as a polyol component for the synthesis of a polyurethane network, which is stable under ambient conditions but degrades rapidly under acidic conditions. [ABSTRACT FROM AUTHOR]

Glycidyltosylat scheint aufgrund der Tosylat‐Abgangsgruppe ein durch nukleophile Initiatoren nicht polymerisierbares Epoxid zu sein. Mit dem monomeraktivierten Mechanismus kann dieses ungewöhnliche Monomer jedoch mit Ethylenoxid (EO) bzw. Propylenoxid (PO) copolymerisiert werden, wobei Copolymere mit 7 bis 25 % eingebauten Tosylat‐Gruppen erhalten werden. Die Mikrostruktur der Copolymere wurde mittels 1H‐NMR‐Spektroskopie in situ untersucht und auch die Copolymerisationsparameter bestimmt. Die quantitative nukleophile Substitution der Tosylatfunktionalität wird an mehreren Beispielen gezeigt. Diese neue Struktur ermöglicht den Zugang zu einer Vielfalt funktionalisierter Polyether, die durch herkömmliche oxyanionische Polymerisation nicht synthetisiert werden können. [ABSTRACT FROM AUTHOR]

Glycidyl tosylate appears to be a non‐polymerizable epoxide when nucleophilic initiators are used because of the excellent leaving group properties of the tosylate. However, using the monomer‐activated mechanism, this unusual monomer can be copolymerized with ethylene oxide (EO) and propylene oxide (PO), respectively, yielding copolymers with 7–25 % incorporated tosylate‐moieties. The microstructure of the copolymers was investigated via in situ 1H NMR spectroscopy, and the reactivity ratios of the copolymerizations have been determined. Quantitative nucleophilic substitution of the tosylate‐moiety is demonstrated for several examples. This new structure provides access to a library of functionalized polyethers that cannot be synthesized by conventional oxyanionic polymerization. [ABSTRACT FROM AUTHOR]

Fluctuation correlation spectroscopy (FCS) is a well-established analytical technique traditionally used to monitor molecular diffusion in dilute solutions, the dynamics of chemical reactions, and molecular processes inside living cells. In this review, we present the recent use of FCS for measuring the size of colloidal nanoparticles in solution. We review the theoretical basis and experimental implementation of this technique and its advantages and limitations. In particular, we show examples of the use of FCS to measure the size of gold nanoparticles, monitor the rotational dynamics of gold nanorods, and investigate the formation of protein coronas on nanoparticles. [ABSTRACT FROM AUTHOR]

Block copolymers of polyisoprene and polystyrene are key materials for polymer nanostructures as well as for several commercially established thermoplastic elastomers. In a combined experimental and kinetic Monte Carlo simulation study, the direct (i.e., statistical) living anionic copolymerization of a mixture of isoprene (I) and 4-methylstyrene (4MS) in nonpolar media was investigated on a fundamental level. In situ ¹H NMR spectroscopy enabled to directly monitor gradient formation during the copolymerization and to determine the nature of the gradient. In addition, a precise comparison with the established copolymerization of isoprene and styrene (I/S) was possible. Statistical copolymerization in both systems leads to tapered block copolymers due to an extremely slow crossover from isoprene to the styrenic monomer. For the system I/4MS the determination of the reactivity ratios shows highly disparate values with rI = 25.4 and r4MS = 0.007, resulting in a steep gradient of the comonomer composition. The rate constants determined from online NMR studies were used for a kinetic Monte Carlo simulation, revealing structural details, such as the distribution of the homopolymer sequences for both blocks, which are a consequence of the peculiar kinetics of the diene/styrene systems. DFT calculations were used to compare the established copolymerization of isoprene and styrene with the isoprene/4-methylstyrene system. A variety of gradient copolymers differing in molecular weight and monomer feed composition were synthesized, confirming strong microphase segregation as a consequence of the blocklike structure. The one-pot synthesis of such tapered block copolymers, avoiding high vacuum or break-seal techniques, is a key advantage for the preparation of ultrahigh molecular weight block copolymers (Mn > 1.2 x 106 g/mol) in one synthetic step. These materials show microphase-segregated bulk structures like diblock copolymers prepared by sequential block copolymer synthesis. Because of the living nature of the tapered block copolymer structures, a vast variety of complex structures are accessible by the addition of further monomers or monomer mixtures in subsequent steps. [ABSTRACT FROM AUTHOR]

We introduce a two-step strategy for the synthesis of linear polyglycerols ( lin PG-OH x /OMe y ) with an adjustable degree of methylation ( y = D M 100 ). Ethoxy ethyl glycidyl ether (EEGE) and glycidyl methyl ether (GME) were copolymerized via the “activated monomer” polymerization technique, using tetraoctylammonium bromide (NOct 4 Br) as an initiator and triisobutylaluminum ( i -Bu 3 Al) as a catalyst under mild conditions. Subsequent acidic cleavage of the acetal protective groups generates linear polyglycerols with different degree of methylation (DM) by varying the GME comonomer content between 10 and 91%. Size exclusion chromatography (SEC) evidenced good control over molecular weight and narrow to moderate polydispersity (PDI = 1.2–1.8). 1 H NMR spectroscopy confirmed ideally random copolymerization of EEGE and GME ( in situ 1 H-NMR kinetics) and provided perfect agreement of the comonomer content with the targeted values. Thermoresponsive behavior in solution and lowering of cloud points with increasing degree of methylation was observed. Furthermore, the differently methylated polyglycerols were investigated with respect to their rheological properties in the melt. Comparison with the fully hydroxylated and permethylated polyglycerol provides new insights into the dynamic behavior of functional polyethers. A tremendous influence of DM on zero-shear viscosity and differences of up to 5 decades were observable at the same reference temperature (273 K). The trend of glass transition temperature and zero-shear viscosity in dependency of degree of methylation was described by mixing rules. To understand the changes in zero-shear viscosity, the “sticky” Rouse model was applied and led to an estimated association lifetime of stickers, i.e. hydroxyl groups of τ s = 4.9 ± 1.8 μ s . [ABSTRACT FROM AUTHOR]