Synthesis Of Miktoarm Star Polymers Research Articles

Modulating Ligand-Exchange Dynamics on Metal-Organic Polyhedra for Reversible Sorting and Hybridization of Miktoarm Star Polymers.

The precise synthesis of miktoarm star polymers (MSPs) remains one of the great challenges in synthetic chemistry due to the difficulty in locating appropriate structural templates and polymer grafting/growing strategies with high selectivity and efficiency. Herein, ≈2 nm metal-organic polyhedra (MOPs), constructed from the coordination of isophthalic acid (IPA) and Cu2+ , are applied as templates for the precise synthesis of 24-arm MSPs for their unique logarithmic ligand-exchange dynamics. Six different polymers are prepared with IPA as an end group and they further coordinated with Cu2+ to afford the corresponding 24-arm star homo-polymers. MSPs can be obtained by mixing targeted homo-arm star polymers in solutions upon thermal annealing. The compositions of MSPs can be facilely and precisely tuned by the recipe of the star polymer mixtures used. Interestingly, the obtained MSPs can be sorted into homo-arm star polymers through a typical solvent extraction procedure. The hybridization and sorting process can be reversibly conducted through the cycle of thermal annealing and solvent treatment. The complex coordination framework not only opens new avenues for the facile and precise synthesis of MSPs and MOPs with hybrid functionalities, but also provides the capability to design sustainable polymer systems.

Modulating Ligand‐Exchange Dynamics on Metal‐Organic Polyhedra for Reversible Sorting and Hybridization of Miktoarm Star Polymers

AbstractThe precise synthesis of miktoarm star polymers (MSPs) remains one of the great challenges in synthetic chemistry due to the difficulty in locating appropriate structural templates and polymer grafting/growing strategies with high selectivity and efficiency. Herein, ≈2 nm metal‐organic polyhedra (MOPs), constructed from the coordination of isophthalic acid (IPA) and Cu2+, are applied as templates for the precise synthesis of 24‐arm MSPs for their unique logarithmic ligand‐exchange dynamics. Six different polymers are prepared with IPA as an end group and they further coordinated with Cu2+ to afford the corresponding 24‐arm star homo‐polymers. MSPs can be obtained by mixing targeted homo‐arm star polymers in solutions upon thermal annealing. The compositions of MSPs can be facilely and precisely tuned by the recipe of the star polymer mixtures used. Interestingly, the obtained MSPs can be sorted into homo‐arm star polymers through a typical solvent extraction procedure. The hybridization and sorting process can be reversibly conducted through the cycle of thermal annealing and solvent treatment. The complex coordination framework not only opens new avenues for the facile and precise synthesis of MSPs and MOPs with hybrid functionalities, but also provides the capability to design sustainable polymer systems.

One-Pot Synthesis of Miktoarm Star Polymers Based on Orthogonal Metal–Ligand Interactions

Miktoarm star polymers are a particular type of branched polymers featuring a star-shaped architecture with arms based on different polymer types. Such materials exhibit unique thermal, mechanical, and self-assembly properties. Hence, this polymer class is of great interest in different research fields. So far, the synthesis of these entities can be rather challenging, particularly applying covalent strategies for linking of the different polymers. Thus, an approach for the synthesis of such polymer architectures is presented using orthogonal metal–ligand interactions to connect the different building blocks, resulting in a miktoarm topology. The obtained structures are investigated via diffusion-ordered nuclear magnetic resonance spectroscopy, by analytical ultracentrifugation and dynamic light scattering.

Polymersomes: Soft Nanoparticles from Miktoarm Stars for Applications in Drug Delivery.

Self-assembly of amphiphilic macromolecules has provided an advantageous platform to address significant issues in a variety of areas, including biology. Such soft nanoparticles with a hydrophobic core and hydrophilic corona, referred to as micelles, have been extensively investigated for delivering lipophilic therapeutics by physical encapsulation. Polymeric vesicles or polymersomes with similarities in morphology to liposomes continue to play an essential role in understanding the behavior of cell membranes and, in addition, have offered opportunities in designing smart nanoformulations. With the evolution in synthetic methodologies to macromolecular precursors, the construction of such assemblies can now be modulated to tailor their properties to match desired needs. This review brings into focus the current state-of-the-art in the design of polymersomes using amphiphilic miktoarm star polymers through a detailed analysis of the synthesis of miktoarm star polymers with tuned lengths of varied polymeric arms, their self-assembly, and applications in drug delivery.

Synthesis of functional miktoarm star polymers in an automated parallel synthesizer

• Synthesis of miktoarm star polymers with functionalized peptide arms was optimized. • Miktoarm star polymers synthesis was executed in an automated parallel synthesizer. • The described methods may potentiate the research and development of these polymers. A feasibility study for the synthesis of well-defined miktoarm star polymers containing peptide arms in an automated parallel synthesizer is reported. A series of linear homo- and block (co–)polymers were prepared in the presence of commercial or peptide-functionalized reversible addition-fragmentation chain transfer (RAFT) agents. Thereafter, miktoarm star polymers were obtained by cross-linking different combinations of the abovementioned linear polymers using N, N '-bis(acryloyl)cystamine (BAC) as a redox responsive cross-linker. The described automated synthesis can be regarded as a proof-of-principle technique that next to emerging automated polymer purification and machine learning approaches could be useful to potentiate the development of autonomous methods for accessing systematic and comprehensive (peptide-)functionalized star polymer libraries. With these approaches hundreds of candidates of these complex polymer architectures could be rapidly synthesized, screened and optimized for different applications.

Facile synthesis of amphiphilic AB3 and A3B miktoarm PeptoMiktoStars

Amphiphilic miktoarm star copolymers have a unique internal structure and many attractive properties with respect to solution self-assembly, such as a high density of internal and peripheral functionalities, low CMC values, and high loading efficiency. However, compared to their linear analogs, the complex architecture demands asymmetric polymer arms emanating from a single core, which poses a significant synthetic challenge. Herein, we demonstrate an approach for the synthesis of polypept(o)ide-based AB3- and A3B-type miktoarm PeptoStars consisting of polypeptidic poly(γ-benzyl-l-glutamate (pGlu(OBn)) as the hydrophobic A arm and polypeptoidic polysarcosine (pSar) as the hydrophilic B arm. These structures, which are completely derived from endogenous amino acids, were realized by the core-first method using a tetrafunctional initiator and the corresponding N-carboxyanhydrides (NCAs) via a controlled, living nucleophilic ring-opening polymerization (ROP). The asymmetric architecture was achieved through an orthogonal protecting group strategy with multiple protection/deprotection steps. Characterization via 1H NMR-, 1H DOSY-spectroscopy, and size-exclusion chromatography (SEC) indicate the presence of well-formed miktoarm PeptoStars with low dispersities (Đ = 1.09–1.14), the precise control over the degree of polymerization and Poisson-like molecular weight distributions. Schwiertz et al. report on the synthesis of miktoarm star polymers based on polypept(o)ides by nucleophilic ring opening polymerization of N-carboxyanhydrides. The reported procedures allow for precise control over chain length, number of arms and end group functionality.

A New Approach for the Synthesis of Miktoarm Star Polymers Through a Combination of Thiol–Epoxy “Click” Chemistry and ATRP/Ring‐Opening Polymerization Techniques

ABSTRACTA new approach was developed for synthesis of certain A3B3‐type of double hydrophilic or amphiphilic miktoarm star polymers using a combination of “grafting onto” and “grafting from” methods. To achieve the synthesis of desired miktoarm star polymers, acetyl protected poly(ethylene glycol) (PEG) thiols (Mn = 550 and 2000 g mol−1) were utilized to generate A3‐type of homoarm star polymers through an in situ protective group removal and a subsequent thiol–epoxy “click” reaction with a tris‐epoxide core viz. 1,1,1‐tris(4‐hydroxyphenyl)ethane triglycidyl ether. The secondary hydroxyl groups generated adjacent to the core upon the thiol–epoxy reaction were esterified with α‐bromoisobutyryl bromide to install atom transfer radical polymerization (ATRP) initiating sites. ATRP of N‐isopropylacrylamide (NIPAM) using the three‐arm star PEG polymer fitted with ATRP initiating sites adjacent to the core afforded A3B3‐type of double hydrophilic (PEG)3[poly(N‐isopropylacrylamide)] (PNIPAM)3 miktoarm star polymers. Furthermore, the generated hydroxyl groups were directly used as initiator for ring‐opening polymerization of ε‐caprolactone to prepare A3B3‐type of amphiphilic (PEG)3[poly(ε‐caprolactone)]3 miktoarm star polymers. The double hydrophilic (PEG)3(PNIPAM)3 miktoarm star polymers showed lower critical solution temperature around 34 °C. The preliminary transmission electron microscopy analysis indicated formation of self‐assembly of (PEG)3(PNIPAM)3 miktoarm star polymer in aqueous solution. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 146–156

Synthesis and characterization of amphiphilic miktoarm star polymers based on sydnone-maleimide double cycloaddition

The synthesis of miktoarm star polymers based on sydnone-maleimide double cycloaddition (SMDC) via three approaches.

Successive Synthesis of Miktoarm Star Polymers Having up to Seven Arms by a New Iterative Methodology Based on Living Anionic Polymerization Using a Trifunctional Lithium Reagent

A new stepwise iterative methodology based on living anionic polymerization using a trifunctional lithium reagent substituted with trimethylsilyl (TMS), tert-butyldimethylsilyl (TBDMS), and tetrahydropyranyl (THP) ethers of protected hydroxyl functionalities has been developed in order to obtain synthetically challenging many-armed μ-star polymers. In each reaction sequence of the new methodology, these three ether functions were selectively deprotected in turn under carefully selected conditions as designed, followed by conversion to three α-phenyl acrylate (PA) reaction sites step by step at different reaction stages. They were used for the introduction of two different arm segments and the reintroduction of the above same three ethers. This reaction sequence was repeated three times to successively synthesize 3-arm ABC, 4-arm ABCD, 5-arm ABCDE, 6-arm ABCDEF, and 7-arm ABCDEFG μ-star polymers with well-defined structures. Herein, the A, B, C, D, E, F, and G arms were poly(cyclohexyl methacrylate), polys...

Precise Synthesis of Miktoarm Star Polymers by Using a New Dual-Functionalized 1,1-Diphenylethylene Derivative in Conjunction with Living Anionic Polymerization System

The general utility of a 1,1-diphenylethylene (DPE) derivative substituted with trimethylsilyl- and tert-butyldimethylsilyl-protected hydroxyl functionalities, as a new dual-functionalized core agent in conjunction with a living anionic polymerization system, has been demonstrated by the successful synthesis of various well-defined 3-arm ABC and 4-arm ABCD μ-star polymers. Two different protected hydroxyl functionalities were progressively deprotected to generate hydroxyl groups, followed by conversion to α-phenyl acrylate (PA) functions at separate stages, and the PA functions were reacted with appropriate living anionic polymers to result in the above μ-stars. In order to further synthesize μ-star polymers with five or more arms, a new iterative methodology using a functional DPE anion derived from the above DPE derivative has been developed. The reaction system of this methodology is designed in such a way that the PA function used as the reaction site is regenerated after the introduction of an arm segment in each reaction sequence, and this sequence, consisting of “arm introduction and regeneration of the PA reaction site”, is repeatable. With this methodology, a series of new well-defined μ-star polymers up to a 5-arm ABCDE type, composed of all different methacrylate-based polymer segments, were successfully synthesized for the first time.