Organocatalytic Ring-Opening Polymerization of N-Acylated-1,4-oxazepan-7-ones Toward Well-Defined Poly(ester amide)s: Biodegradable Alternatives to Poly(2-oxazoline)s

Heteroatom Substitution Strategy Modulates Thermodynamics Towards Chemically Recyclable Polyesters and Monomeric Unit Sequence by Temperature Switching

In this paper, we proposed a heteroatom substitution strategy (HSS) in the δ-valerolactone (VL) system to modulate thermodynamics toward chemically recyclable polyesters. Three VL-based monomers containing different heteroatoms (M1 (N), M2 (S), and M3 (O)), instead of C-5 carbon, were designed and synthesized to verify our proposed HSS. All three monomers undergo organocatalytic living/controlled ROP and controllable depolymerization. Impressively, the resulting P(M1) achieved over 99 % monomer recovery under both mild solution depolymerization and high vacuum pyrolysis conditions without any side reactions, and the recycled monomers can be polymerized again forming new polymers. The systematic study of the relationship between heteroatom substitution and recyclability shows that introducing heteroatoms does change the thermodynamics of the monomers (ΔHp o, ΔSp o and Tc values), thereby adjusting the polymerizability and depolymerizability. DFT calculations found that the introduction of heteroatoms adjusts the ring strain by changing the angular strain of the monomers, and the order of their angular strain (M2>M1>M3) is consistent with the order of the experimentally obtained enthalpy change. Notably, the one-pot/one-step copolymerization of two of each of the three monomers enables the synthesis of sequence-controlled copolymers from gradient to random to block structures, by simply switching the copolymerization temperature.

Multiphasic Coacervates Assembled by Hydrogen Bonding and Hydrophobic Interactions

Coacervation has emerged as a prevalent mechanism to compartmentalize biomolecules in living cells. Synthetic coacervates help in understanding the assembly process and mimic the functions of biological coacervates as simplified artificial systems. Though the molecular mechanism and mesoscopic properties of coacervates formed from charged coacervates have been well investigated, the details of the assembly and stabilization of nonionic coacervates remain largely unknown. Here, we describe a library of coacervate-forming polyesteramides and show that the water-tertiary amide bridging hydrogen bonds and hydrophobic interactions stabilize these nonionic, single-component coacervates. Analogous to intracellular biological coacervates, these coacervates exhibit "liquid-like" features with low viscosity and low interfacial energy, and form coacervates with as few as five repeating units. By controlling the temperature and engineering the molar ratio between hydrophobic interaction sites and bridging hydrogen bonding sites, we demonstrate the tuneability of the viscosity and interfacial tension of polyesteramide-based coacervates. Taking advantage of the differences in the mesoscopic properties of these nonionic coacervates, we engineered multiphasic coacervates with core-shell architectures similar to those of intracellular biological coacervates, such as nucleoli and stress granule-p-body complexes. The multiphasic structures produced from these synthetic nonionic polyesteramide coacervates may serve as a valuable tool for investigating physicochemical principles deployed by living cells to spatiotemporally control cargo partitioning, biochemical reaction rates, and interorganellar signal transport.

Block copolymers comprising degradable poly(2-ethyl-2-oxazoline) analogues via copper-free click chemistry

We present the synthesis development of amphiphilic, degradable poly(2-ethyl-2-oxazoline) (PEtOx) analogue block copolymers in a modular fashion utilizing the strain-promoted azide–alkyne cycloaddition (SPAAC).

Heterotellurium-containing macrocycles towards degradable tellurium-functionalized polymers

We first disclose a facile strategy to synthesize a heterotellurium-containing macrocycle series, and then well-defined degradable poly(telluride-carbonate)s were obtained by ring-opening polymerization.

Alternating Ring-Opening Metathesis Polymerization Provides Easy Access to Functional and Fully Degradable Polymers

Polymers with hydrolyzable groups in their backbones have numerous potential applications in biomedicine, lithography, energy storage and electronics. In this study, acetal and ester functionalities were incorporated into the backbones of copolymers by means of alternating ring-opening metathesis polymerization catalyzed by third-generation Grubbs ruthenium catalyst. Specifically, combining large-ring (7-10 atoms) cyclic acetal or lactone monomers with bicyclo[4.2.0]oct-1(8)-ene-8-carboxamide monomers provided perfectly alternating copolymers with acetal or ester functionality in the backbones and low to moderate molecular weight distribution (Đ M = 1.2-1.6). Copolymers containing ester and acetal backbones hydrolyzed to significant extent under basic condition (pH 13) and acidic conditions (pH ≤ 5) respectively to yield the expected by-products within 30 hours at moderate temperature. Unlike the copolymer with all-carbon backbone, copolymers with heteroatom-containing backbone exhibited viscoelastic behavior with crossover frequency which decreases as the size of the R group on the acetal increases. In contrast, the glass transition temperature (T g) decreases as the size of the R group decreases. The rate of hydrolysis of the acetal copolymers was also dependent on the R group. Thus, ruthenium-catalyzed alternating ring-opening metathesis copolymerization provides heterofunctional copolymers whose degradation rates, glass transition temperatures, and viscoelastic moduli can be controlled.

Lipase-catalysed polycondensation of levulinic acid derived diol-diamide monomers: access to new poly(ester-co-amide)s

A new family of biobased poly(ester-co-amide)s is reported from the enzymatic polycondensation of a library of levulinic acid derived diol-diamide monomers with diesters.