Low-Fouling Fluoropolymers for Bioconjugation and In Vivo Tracking

The conjugation of hydrophilic low-fouling polymers to therapeutic molecules and particles is an effective approach to improving their aqueous stability, solubility, and pharmacokinetics. Recent concerns over the immunogenicity of poly(ethylene glycol) has highlighted the importance of identifying alternative low fouling polymers. Now, a new class of synthetic water-soluble homo-fluoropolymers are reported with a sulfoxide side-chain structure. The incorporation of fluorine enables direct imaging of the homopolymer by ¹⁹F MRI, negating the need for additional synthetic steps to attach an imaging moiety. These self-reporting fluoropolymers show outstanding imaging sensitivity and remarkable hydrophilicity, and as such are a new class of low-fouling polymer for bioconjugation and in vivo tracking.     

Influence of donor–acceptor conjugation between thiophene‐phthalazinone structures containing Sp3 CN bond on the frontier orbital levels and optic–electronic properties

Herein, an electron‐deficient phthalazinone unit containing a unique Sp³ hybrid nitrogen atom as an acceptor to cut off the ether bond was presented and three Donor–Acceptor (D–A) conjugated fluoropolymers via Classical Aromatic Nucleophilic Displacement Polymerization (CANDP) method were successfully synthesized. These polymers exhibit excellent thermostability. The 5% weight loss temperature of PDT2TF under nitrogen atmosphere is high, up to 470 °C. This is due to that the D–A conjugation between thiophene‐phthalazinone units affects its resonance energy and stabilizes the thiophene‐phthalazinone structures. These three fluoropolymers show strong absorptions and fluorescence in visible light region both in solution and thin film states. The band gaps (E_g) of these polymers are narrower than that of their corresponding di‐NH capped monomers, owing to the good electronic communication properties of the Sp³ nitrogen atom in the phthalazinone unit. The E_g value of PDT3TF is decreased to 2.03 eV. These results indicate that phthalazinone unit is an efficient acceptor and could exhibit strong D–A effect with thiophene unit. Also, the Sp³ nitrogen atom in the phthalazinone shows good electronic wave function and charge transport properties. This facile CANDP synthetic method combined with Sp³ C? N bond linked electron‐deficient phthalazinone unit affords polymers with controllable photoelectric properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3470–3483     

Linking polythiophene chains with vinylene‐bridges: A way to improve charge transport in polymer field‐effect transistors

A series of novel branched polythiophene derivatives bearing different densities of vinylene‐bridges as linking chains were synthesized by a general synthetic strategy. The organic field‐effect transistors, which were fabricated by spin‐coating the polymer solutions onto octadecyltrichlorosilane‐modified SiO₂/Si substrates with top‐contact configuration, afforded a high mobility of 8.0 × 10^?3 cm² V^?1 s^?1 with an on/off ratio greater than 10⁴ and a threshold voltage of about ?3 V in saturation regime. The devices based on these polymers possessed better performance than those of polymers without conjugated bridges and polymers with longer conjugated bridges. These results demonstrated that the combination of conjugated polythiophene backbones and vinylene‐bridges would improve the carrier mobility. As an emerging class of conjugated materials, polymers with vinylene‐bridges as linking chains would open up new opportunities in organic electronics, and their applications in organic electronics are promising. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1381–1392, 2009     

Self‐assembly of star‐shaped polystyrene‐block‐polypeptide copolymers synthesized by the combination of atom transfer radical polymerization and ring‐opening living polymerization of α‐amino acid‐N‐carboxyanhydrides

The self‐assembling nature and phase‐transition behavior of a novel class of triarm, star‐shaped polymer–peptide block copolymers synthesized by the combination of atom transfer radical polymerization and living ring‐opening polymerization of α‐amino acid‐N‐carboxyanhydride are demonstrated. The two‐step synthesis strategy adopted here allows incorporating polypeptides into the usual synthetic polymers via an amido–amidate nickelacycle intermediate, which is used as the macroinitiator for the growth of poly(γ‐benzyl‐L ‐glutamate). The characterization data are reported from analyses using gel permeation chromatography and infrared, ¹H NMR, and ¹³C NMR spectroscopy. This synthetic scheme grants a facile way to prepare a wide range of polymer–peptide architectures with perfect microstructure control, preventing the formation of homopolypeptide contaminants. Studies regarding the supramolecular organization and phase‐transition behavior of this class of polymer‐block‐polypeptide copolymers have been accomplished with X‐ray diffraction, infrared spectroscopy, and thermal analyses. The conformational change of the peptide segment in the block copolymer has been investigated with variable‐temperature infrared spectroscopy. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2774–2783, 2006     

Zinc‐Catalyzed Depolymerization of End‐of‐Life Polysiloxanes

Polymers occupy an important role in our current society. Besides their great success, an issue is the accumulation of huge amounts of end‐of‐life polymers. Currently, the waste management is based primarily on landfills, thermal recycling, and downcycling. Notably, only a small portion of end‐of‐life materials is recycled by depolymerization, which refers to the creation of synthetic precursors that can be polymerized to new polymers to close the cycle. Widely used polymers in modern times are silicones (polysiloxanes), the intrinsic properties of which make their depolymerization demanding; only a few high‐temperature or less environmentally friendly processes have been reported. In this regard, we have established an efficient low‐temperature protocol for the depolymerization of silicones with benzoyl fluoride in the presence of cheap zinc salts as precatalysts to yield defined products. Notably, the products can be useful synthetic precursors for the preparation of new polymers, so that an overall recycling process is feasible.     

Highly Conductive Anion‐Exchange Membranes from Microporous Tröger's Base Polymers

The development of polymeric anion‐exchange membranes (AEMs) combining high ion conductivity and long‐term stability is a major challenge for materials chemistry. AEMs with regularly distributed fixed cationic groups, based on the formation of microporous polymers containing the V‐shape rigid Tröger's base units, are reported for the first time. Despite their simple preparation, which involves only two synthetic steps using commercially available precursors, the polymers provide AEMs with exceptional hydroxide conductivity at relatively low ion‐exchange capacity, as well as a high swelling resistance and chemical stability. An unprecedented hydroxide conductivity of 164.4 mS cm^?1 is obtained at a relatively a low ion‐exchange capacity of 0.82 mmol g^?1 under optimal operating conditions. The exceptional anion conductivity appears related to the intrinsic microporosity of the charged polymer matrix, which facilitates rapid anion transport.     

High‐Temperature and High‐Energy‐Density Dipolar Glass Polymers Based on Sulfonylated Poly(2,6‐dimethyl‐1,4‐phenylene oxide)

A new class of high‐temperature dipolar polymers based on sulfonylated poly(2,6‐dimethyl‐1,4‐phenylene oxide) (SO₂‐PPO) was synthesized by post‐polymer functionalization. Owing to the efficient rotation of highly polar methylsulfonyl side groups below the glass transition temperature (T_g≈220 °C), the dipolar polarization of these SO₂‐PPOs was enhanced, and thus the dielectric constant was high. Consequently, the discharge energy density reached up to 22 J cm^?3. Owing to its high T_g , the SO₂‐PPO₂₅ sample also exhibited a low dielectric loss. For example, the dissipation factor (tan δ) was 0.003, and the discharge efficiency at 800 MV m^?1 was 92 %. Therefore, these dipolar glass polymers are promising for high‐temperature, high‐energy‐density, and low‐loss electrical energy storage applications.     

Triazole‐Based One‐Dimensional Spin‐Crossover Coordination Polymers

One‐dimensional coordination Fe^II polymers constructed through triple N¹,N²‐1,2,4‐triazole bridges form a unique class of spin‐crossover materials, the synthetic versatility of which allows tuning the spin‐crossover properties, the design of gels, films, liquid crystals, and nanoparticles and single‐particle addressing. This Minireview provides the first complete overview of these very attractive switchable materials and their most recent developments.     

Polymer Brushes Showing Non‐Fouling in Blood Plasma Challenge the Currently Accepted Design of Protein Resistant Surfaces

Ultra‐low‐fouling poly[N‐(2‐hydroxypropyl) methacrylamide] (poly(HPMA)) brushes have been synthesized for the first time. Similar to the so far only ultra‐low‐fouling surface, poly(carboxybetaine acrylamide), the level of blood plasma fouling was below the detection limit of surface plasmon resonance (SPR, 0.03 ng · cm⁻²) despite being a hydrogen bond donor and displaying a moderate wettability, thus challenging the currently accepted views for the design of antifouling properties. The antifouling properties were preserved even after two years of storage. To demonstrate the potential of poly(HPMA) brushes for the preparation of bioactive ultra‐low fouling surfaces a label‐free SPR immunosensor for detection of G Streptococcus was prepared.

     

Topotactic Synthesis of Phosphabenzene‐Functionalized Porous Organic Polymers: Efficient Ligands in CO2 Conversion

Progress toward the preparation of porous organic polymers (POPs) with task‐specific functionalities has been exceedingly slow—especially where polymers containing low‐oxidation phosphorus in the structure are concerned. A two‐step topotactic pathway for the preparation of phosphabenzene‐based POPs (Phos‐POPs) under metal‐free conditions is reported, without the use of unstable phosphorus‐based monomers. The synthetic route allows additional functionalities to be introduced into the porous polymer framework with ease. As an example, partially fluorinated Phos‐POPs (F‐Phos‐POPs) were obtained with a surface area of up to 591 m² g^?1. After coordination with Ru species, a Ru/F‐Phos‐POPs catalyst exhibited high catalytic efficiency in the formylation of amines (turnover frequency up to 204 h^?1) using a CO₂/H₂ mixture, in comparison with the non‐fluorinated analogue (43 h^?1) and a Au/TiO₂ heterogeneous catalysts reported previously (<44 h^?1). This work describes a practical method for synthesis of porous organic phosphorus‐based polymers with applications in transition‐metal‐based heterogeneous catalysis.     

Chain‐Growth Click Polymerization of AB2 Monomers for the Formation of Hyperbranched Polymers with Low Polydispersities in a One‐Pot Process

Hyperbranched polymers are important soft nanomaterials but robust synthetic methods with which the polymer structures can be easily controlled have rarely been reported. For the first time, we present a one‐pot one‐batch synthesis of polytriazole‐based hyperbranched polymers with both low polydispersity and a high degree of branching (DB) using a copper‐catalyzed azide–alkyne cycloaddition (CuAAC) polymerization. The use of a trifunctional AB₂ monomer that contains one alkyne and two azide groups ensures that all Cu catalysts are bound to polytriazole polymers at low monomer conversion. Subsequent CuAAC polymerization displayed the features of a “living” chain‐growth mechanism with a linear increase in molecular weight with conversion and clean chain extension for repeated monomer additions. Furthermore, the triazole group in a linear (L) monomer unit complexed Cu^I, which catalyzed a faster reaction of the second azide group to quickly convert the L unit into a dendritic unit, producing hyperbranched polymers with DB=0.83.     

Antimicrobial Poly(2‐methyloxazoline)s with Bioswitchable Activity through Satellite Group Modification

Biocides are widely used for preventing the spread of microbial infections and fouling of materials. Since their use can build up microbial resistance and cause unpredictable long‐term environmental problems, new biocidal agents are required. In this study, we demonstrate a concept in which an antimicrobial polymer is deactivated by the cleavage of a single group. Following the satellite group approach, a biocidal quaternary ammonium group was linked through a poly(2‐methyloxazoline) to an ester satellite group. The polymer with an octyl‐3‐propionoate satellite group shows very good antimicrobial activity against Gram‐positive bacterial strains. The biocidal polymer was also found to have low hemotoxicity, resulting in a high HC₅₀/MIC value of 120 for S. aureus. Cleaving the ester satellite group resulted in a 30‐fold decrease in antimicrobial activity, proving the concept valid. The satellite group could also be cleaved by lipase showing that the antimicrobial activity of the new biocidal polymers is indeed bioswitchable.     

Conjugated polymers based on 1,8‐naphthalene monoimide with high electron mobility

1,4,8,9‐Naphthalene diimides (NDIs) with strong electron accepting ability and high stability are excellent building blocks for semiconductor polymers. However, 1,8‐naphthalene monoimide (NMI) with similar structure and energy levels as that of NDI has never been used to construct conjugated polymers because of synthetic difficulty. Herein, 3,6‐dibromo‐NMI (DBNMI) with bulky alkyl groups was obtained effectively in a four‐step synthesis, and three donor‐acceptor (D‐A) type conjugated polymers based on NMI were firstly prepared. These polymers have strong absorption in the range of 300–600 nm, low LUMO level of 3.68 eV, and moderate bandgaps of 2.18 eV. Space charge limiting current measurements indicate these polymers are typical electron transporting materials, and the highest electron mobility is up to 5.8 × 10⁻³ cm² V⁻¹ s⁻¹, which is close to the star acceptor based on NDI (N2200, 5.0 × 10⁻³ cm² V⁻¹ s⁻¹). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 276–281     

Studies of electroosmotic flow and the effects of protein adsorption in plasma‐polymerized microchannel surfaces

This paper presents a study of EOF properties of plasma‐polymerized microchannel surfaces and the effects of protein (fibrinogen and lysozyme) adsorption on the EOF behavior of the surface‐modified microchannels. Three plasma polymer surfaces, i.e. tetraglyme, acrylic acid and allylamine, are tested. Results indicate EOF suppression in all plasma‐coated channels compared with the uncoated glass microchannel surfaces. The EOF behaviors of the modified microchannels after exposure to protein solutions are also investigated and show that even low levels of protein adsorption can significantly influence EOF behavior, and in some cases, result in the reversal of flow. The results also highlight that EOF measurement can be used as a method for detecting the presence of proteins within microchannels at low surface coverage (<1 ng/cm² on glass). Critically, the results illustrate that the non‐fouling tetraglyme plasma polymer is able to sustain EOF. Comparison of the plasma‐polymerized surfaces with conventionally grafted polyelectrolyte surfaces demonstrates the stabilities of the plasma polymer films, enabling multiple EOF runs over 3 days without deterioration in performance. The results of this study clearly demonstrate that plasma polymers enable the surface chemistry of microfluidic devices to be tailored for specific applications. Critically, the deposition of the non‐fouling tetraglyme coating enables stable EOF to be induced in the presence of protein.     

New Classes of Ferromagnetic Materials with Exclusively End‐on Azido Bridges: From Single‐Molecule Magnets to 2 D Molecule‐Based Magnets

A new, flexible synthetic route, which does not require the co‐presence of any organic chelating/bridging ligand but only the “key” precursor Me₃SiN₃, has been discovered and led to a new class of inorganic materials containing exclusively end‐on azido bridges; the reported 3d‐metal clusters and coordination polymers exhibit ferromagnetic, single‐molecule magnet, and long‐range magnetic ordering properties.     

Emerging Synthetic Strategies for Core Cross‐Linked Star (CCS) Polymers and Applications as Interfacial Stabilizers: Bridging Linear Polymers and Nanoparticles

Core cross‐linked star (CCS) polymers become increasingly important in polymer science and are evaluated in many value‐added applications. However, limitations exist to varied degrees for different synthetic methods. It is clear that improvement in synthetic efficiency is fundamental in driving this field moving even further. Here, the most recent advances are highlighted in synthetic strategies, including cross‐linking with cross‐linkers of low solubility, polymerization‐induced self‐assembly in aqueous‐based heterogeneous media, and cross‐linking via dynamic covalent bonds. The understanding of CCS polymers is also further refined to advocate their role as an intermediate between linear polymers and polymeric nanoparticles, and their use as interfacial stabilizers is rationalized within this context.

     

Dehydrocoupling and Silazane Cleavage Routes to Organic–Inorganic Hybrid Polymers with NBN Units in the Main Chain

Despite the great potential of both π‐conjugated organoboron polymers and BN‐doped polycyclic aromatic hydrocarbons in organic optoelectronics, our knowledge of conjugated polymers with B?N bonds in their main chain is currently scarce. Herein, the first examples of a new class of organic–inorganic hybrid polymers are presented, which consist of alternating NBN and para‐phenylene units. Polycondensation with B?N bond formation provides facile access to soluble materials under mild conditions. The photophysical data for the polymer and molecular model systems of different chain lengths reveal a low extent of π‐conjugation across the NBN units, which is supported by DFT calculations. The applicability of the new polymers as macromolecular polyligands is demonstrated by a cross‐linking reaction with Zr^IV.     

Synthesis and characterization of N‐substituted hyperbranched polyureas

N,N′‐disubstituted hyperbranched polyureas with methyl, benzyl, and allyl substitutents were synthesized starting from AB₂ monomers based on 3,5‐diamino benzoic acid. Carbonyl azide approach, which generates isocyanate group in situ on thermal decomposition, was used for the protection of isocyanate functional groups. The N‐substituted hyperbranched polymers can be considered as the new class of internally functionalized hyperbranched polyureas wherein the substituent can function either as receptor or as a chemical entity for selective transformations as a tool to tailor the properties. The chain‐ends were also modified by attaching long chain aliphatic groups to fully realize the interior functionalization. This approach opens up a possible synthetic route wherein different functional substituents can be used to generate a library of internally functionalized hyperbranched polymers. All the hyperbranched polyureas were characterized by FTIR, ¹H‐NMR, DSC, TGA, and size exclusion chromatography. Degree of branching in these N,N′‐disubstituted hyperbranched polyureas, as calculated by ¹H‐NMR spectroscopy using model compounds, was found to be lower than the unsubstituted hyperbranched polyurea and is attributed to the lower reactivity of N‐substituted amines compared to that of unsubstituted amines. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5134–5145, 2004     

Photoorganocatalyzed Divergent Reversible-Deactivation Radical Polymerization towards Linear and Branched Fluoropolymers

Topology influences the properties and applications of polymers. Consequently, considerable efforts have been made to control topological structures. In this work, we have developed a photoorganocatalyzed divergent synthetic approach based on reversible-deactivation radical polymerization (RDRP) that enables the preparation of both linear and branched fluoropolymers of low dispersity (Ð), a tunable degree of branching and high chain-end fidelity by exposure to LED light irradiation under metal-free conditions. This method promotes the generation of complicated structures (e.g., necklace-like and mop-like fluoropolymers) via chain-extension photo-RDRP, and provides a novel and versatile platform to access fluoropolymer electrolytes with high Li-ion transference number and good ionic conductivity, which should create improved opportunities for advanced material engineering.     

An Expeditious Multigram‐Scale Synthesis of Lysine Dendrigraft (DGL) Polymers by Aqueous N‐Carboxyanhydride Polycondensation

The synthesis and characterisation of new arborescent architectures of poly(L ‐lysine), called lysine dendrigraft (DGL) polymers, are described. DGL polymers were prepared through a multiple‐generation scheme (up to generation 5) in a weakly acidic aqueous medium by polycondensing N^ε‐trifluoroacetyl‐L ‐lysine‐N‐carboxyanhydride (Lys(Tfa)‐NCA) onto the previous generation G(n?1) of DGL, which was used as a macroinitiator. The first generation employed spontaneous NCA polycondensation in water without a macroinitiator; this afforded low‐molecular‐weight, linear poly(L ‐lysine) G1 with a polymerisation degree of 8 and a polydispersity index of 1.2. The spontaneous precipitation of the growing N^ε‐Tfa‐protected polymer (GnP) ensures moderate control of the molecular weight (with unimodal distribution) and easy work‐up. The subsequent alkaline removal of Tfa protecting groups afforded generation Gn of DGL as a free form (with 35–60 % overall yield from NCA precursor, depending on the DGL generation) that was either used directly in the synthesis of the next generation (G(n+1)) or collected for other uses. Unprotected forms of DGL G1–G5 were characterised by size‐exclusion chromatography, capillary electrophoresis and ¹H NMR spectroscopy. The latter technique allowed us to assess the branching density of DGL, the degree of which (ca. 25 %) turned out to be intermediate between previously described dendritic graft poly(L ‐lysines) and lysine dendrimers. An optimised monomer (NCA) versus macroinitiator (DGL G(n?1)) ratio allowed us to obtain unimodal molecular weight distributions with polydispersity indexes ranging from 1.3 to 1.5. Together with the possibility of reaching high molecular weights (with a polymerisation degree of ca. 1000 for G5) within a few synthetic steps, this synthetic route to DGL provides an easy, cost‐efficient, multigram‐scale access to dendritic polylysines with various potential applications in biology and in other domains.