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1. Linear‐Dendritic Alternating Copolymers

   https://doi.org/10.1002/ange.201903402  

   Sun, Haotian ; Haque, Farihah M. ; Zhang, Yi ; Commisso, Alex ; Mohamed, Mohamed Alaa ; Tsianou, Marina ; Cui, Honggang ; Grayson, Scott M. ; Cheng, Chong ( June 2019 , Angewandte Chemie)

   Herein, the design, synthesis, and characterization of an unprecedented copolymer consisting of alternating linear and dendritic segments is described. First, a 4th‐generation Hawker‐type dendron with two azide groups was synthesized, followed by a step‐growth azide‐alkyne “click” reaction between the 4th‐generation diazido dendron and poly(ethylene glycol) diacetylene to create the target polymers. Unequal reactivity of the functional groups was observed in the step‐growth polymerization. The resulting copolymers, with alternating hydrophilic linear and hydrophobic dendritic segments, can spontaneously associate into a unique type of microphase‐segregated nanorods in water.

    

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2. Chain‐growth polymerization of azide–alkyne difunctional monomer: Synthesis of star polymer with linear polytriazole arms from a core

   https://doi.org/10.1002/pola.29440  

   Gan, Weiping ; Cao, Xiaosong ; Shi, Yi ; Gao, Haifeng ( July 2019 , Journal of Polymer Science)

   This article reports a chain‐growth coupling polymerization of AB difunctional monomer via copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction for synthesis of star polymers. Unlike our previously reported CuAAC polymerization of AB_n(n ≥ 2) monomers that spontaneously demonstrated a chain‐growth mechanism in synthesis of hyperbranched polymer, the homopolymerization of AB monomer showed a common but less desired step‐growth mechanism as the triazole groups aligned in a linear chain could not effectively confine the Cu catalyst in the polymer species. In contrast, the use of polytriazole‐based core molecules that contained multiple azido groups successfully switched the polymerization of AB monomers into chain‐growth mechanism and produced 3‐arm star polymers and multi‐arm hyperstar polymers with linear increase of polymer molecular weight with conversion and narrow molecular weight distribution, for example,M_w/M_n ~ 1.05. When acid‐degradable hyperbranched polymeric core was used, the obtained hyperstar polymers could be easily degraded under acidic environment, producing linear degraded arms with defined polydispersity. © 2019 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 84–90

    

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3. Physicochemical properties and bio‐interfacial interactions of surface modified PDLLA‐PAMAM linear dendritic block copolymers

   https://doi.org/10.1002/pol.20210448  

   Simms, Briana L. ; Ji, Nan ; Chandrasiri, Indika ; Zia, Mohammad Farid ; Udemgba, Chinwe S. ; Kaur, Ravinder ; Delcamp, Jared H. ; Flynt, Alex ; Tan, Chalet ; Watkins, Davita L. ( July 2021 , Journal of Polymer Science)

   Here, we demonstrate the applicability of self‐assembling linear‐dendritic block copolymers (LDBCs) and their nanoaggregates possessing varied surfaces as therapeutic nanocarriers. These LDBCs are comprised of a hydrophobic, linear polyester chemically coupled to a hydrophilic dendron polyamidoamine (PAMAM)—the latter of which acts as the surface of the self‐assembled nanoaggregate in aqueous media. To better understand how surface charge density affects the overall operability of these nanomaterials, we modified the nanoaggregate surface to yield cationic (NH₃⁺), neutral (OH), and anionic (COO⁻) surfaces. The effect of these modifications on the physicochemical properties (i.e., size, morphology, and surface charge density), colloidal stability, and cellular uptake mechanism of the polymeric nanocarrier were investigated. This comparative study demonstrates the viability of nanoaggregates formed from PDLLA‐PAMAM LDBCs to serve as nanocarriers for applications in drug delivery.

    

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4. Synthesis and characterization of polylactide‐PAMAM “Janus‐type” linear‐dendritic hybrids

   https://doi.org/10.1002/pola.29409  

   Chandrasiri, Indika ; Abebe, Daniel G. ; Gupta, Sudipta ; Williams, Jon Steven Dal ; Rieger, William D. ; Simms, Briana L. ; Yaddehige, Mahesh Loku ; Noh, YeRim ; Payne, Molly E. ; Fortenberry, Alexander W. ; et al ( May 2019 , Journal of Polymer Science Part A: Polymer Chemistry)

   Herein, we present a facile and comprehensive synthetic methodology for the preparation of polyester‐polyamidoamine (PAMAM) (i.e., polyester: polylactide [PLA] (hydrophobic) and polyamidoamine, PAMAM [hydrophilic]) polymers. A library of PLA‐PAMAM linear dendritic block copolymers (LDBCs) in which bothlandd,lpolylactide were employed in mass ratios of 30:70, 50:50, 70:30, and 90:10 (PLA:PAMAM) were synthesized and analyzed. When placed in aqueous media, the immiscibility of the hydrophilic and hydrophobic segments leads to nanophase‐segregation exhibited as the formation of aggregates (e.g., vesicles, worms, and/or micelles). By employing both stereochemical configurations of PLA, the differentiation in mass ratios of PLA‐PAMAM aided in elucidating the structure–property relationships of the LDBC system and provided a means toward the control of nanoparticle morphology. Transmission electron microscopy and dynamic light scattering afford the size and shape of the nanoparticles with diameters ranging from 10.6 for low mass ratios to 122.4 nm for high mass ratios of PLA‐PAMAM and positive zeta‐potential values between +24.7 mV and +48.2 mV. Furthermore, small‐angle X‐ray scattering (SAXS) studies were employed to obtain more detailed information on the morphological assemblies constructed via direct dissolution. Such insights provide a pathway toward nanomaterials with unique morphologies and tunable properties deemed relevant in the development of next generation biomaterials. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1448–1459

    

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5. Heteroacene-Based Amphiphile as a Molecular Scaffold for Bioimaging Probes

   https://doi.org/10.3389/fchem.2021.729125  

   Ranathunge, Tharindu A. ; Yaddehige, Mahesh Loku ; Varma, Jordan H. ; Smith, Cameron ; Nguyen, Jay ; Owolabi, Iyanuoluwani ; Kolodziejczyk, Wojciech ; Hammer, Nathan I. ; Hill, Glake ; Flynt, Alex ; et al ( August 2021 , Frontiers in Chemistry)

   null (Ed.)

   The challenges faced with current fluorescence imaging agents have motivated us to study two nanostructures based on a hydrophobic dye, 6 H -pyrrolo[3,2- b :4,5- b ’]bis [1,4]benzothiazine (TRPZ). TRPZ is a heteroacene with a rigid, pi-conjugated structure, multiple reactive sites, and unique spectroscopic properties. Here we coupled TRPZ to a tert-butyl carbamate (BOC) protected 2,2-bis(hydroxymethyl)propanoic acid (bisMPA) dendron via azide-alkyne Huisgen cycloaddition. Deprotection of the protected amine groups on the dendron afforded a cationic terminated amphiphile, TRPZ-bisMPA . TRPZ-bisMPA was nanoprecipitated into water to obtain nanoparticles (NPs) with a hydrodynamic radius that was <150 nm. For comparison, TRPZ-PG was encapsulated in pluronic-F127 (Mw = 12 kD), a polymer surfactant to afford NPs almost twice as large as those formed by TRPZ-bisMPA . Size and stability studies confirm the suitability of the TRPZ-bisMPA NPs for biomedical applications. The photophysical properties of the TRPZ-bisMPA NPs show a quantum yield of 49%, a Stokes shift of 201 nm (0.72 eV) and a lifetime of 6.3 ns in water. Further evidence was provided by cell viability and cellular uptake studies confirming the low cytotoxicity of TRPZ-bisMPA NPs and their potential in bioimaging. 

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