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Mahesh K Mahanthappa - One of the best experts on this subject based on the ideXlab platform.

  • morphological impact of segment Dispersity in lithium salt doped poly styrene poly ethylene oxide triblock polymers
    Macromolecules, 2019
    Co-Authors: Eric Greve, Mahesh K Mahanthappa
    Abstract:

    We investigate the impact of center segment Dispersity on the phase behavior of 17 lithium salt-doped poly(styrene-block-oligo(ethylene oxide) carbonate-block-styrene) (bSOS) triblock polymers, in which broad Dispersity O blocks (ĐO = Mw/Mn ≈ 1.45) are situated between narrow Dispersity S segments (ĐS ≤ 1.18) with volume fractions fO = 0.33–0.69 and total Mn = 11.6–43.8 kg/mol. Broad Dispersity bSOS triblocks are synthesized by a tandem polycondensation and atom transfer radical polymerization reaction sequence. Using temperature-dependent small-angle X-ray scattering, we map the morphology diagrams for bSOS samples variously doped with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with r = (mol Li+)/(mol ethylene oxide) = 0.00–0.09. As compared to the phase behavior exhibited by 13 LiTFSI-doped, narrow Dispersity SOS triblocks with fO = 0.30–0.58 and Mn = 7.1–45.2 kg/mol, we demonstrate that O segment Dispersity shifts the lamellar morphology window to higher fO/salt and the lamellar microdomains di...

  • morphological impact of segment Dispersity in lithium salt doped poly styrene poly ethylene oxide triblock polymers
    Macromolecules, 2019
    Co-Authors: Eric Greve, Mahesh K Mahanthappa
    Abstract:

    We investigate the impact of center segment Dispersity on the phase behavior of 17 lithium salt-doped poly(styrene-block-oligo(ethylene oxide) carbonate-block-styrene) (bSOS) triblock polymers, in ...

  • Dispersity control in atom transfer radical polymerizations through addition of phenylhydrazine
    Polymer Chemistry, 2018
    Co-Authors: Vivek Yadav, Mahesh K Mahanthappa, Nairah Hashmi, Wenyue Ding, Jacinta C Conrad, Megan L Robertson
    Abstract:

    Molar mass Dispersity in polymers affects a wide range of important material properties, yet there are few synthetic methods that systematically generate unimodal distributions with specifically tailored dispersities. Here, we describe a general method for tuning the Dispersity of polymers synthesized via atom transfer radical polymerization (ATRP). Addition of varying amounts of phenylhydrazine (PH) to the ATRP of tert-butyl acrylate led to significant deviations in the reaction kinetics, yielding poly(tert-butyl acrylate) with dispersities Đ = 1.08–1.80. ATRP reactions in the presence of the reducing agent tin(II) 2-ethylhexanoate, under otherwise comparable reaction conditions, did not drive similar increases in Dispersity. We therefore deduced that PH does not function primarily as a reducing agent in these syntheses. Nuclear magnetic resonance analyses revealed the incorporation of aromatic polymer end-groups upon PH addition, suggesting that the ATRP-active halide termini of the growing polymer chains underwent irreversible nucleophilic substitution reactions with PH that led to chain termination. A kinetic model including this irreversible chain termination by PH was in excellent agreement with experimentally measured reaction kinetics. To demonstrate the generality of this approach, we conducted ATRP syntheses of polystyrene in the presence of PH to achieve dispersities of Đ = 1.07–2.30. This study suggests that PH addition is an effective, facile, and flexible method of Dispersity control in polymers synthesized by ATRP.

  • order and disorder in high χ low n broad Dispersity aba triblock polymers
    Macromolecules, 2017
    Co-Authors: Adam K Schmitt, Mahesh K Mahanthappa
    Abstract:

    Using a combination of small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), we document the composition-dependent morphologies of 39 new poly(lactide-block-1,4-butadiene-block-lactide) (LBL) block polymers, comprising a broad Dispersity B segment (Mn = 4.5–17.7 kg/mol; Đ = Mw/Mn = 1.72–1.88) and narrow Dispersity L end blocks (Mn = 0.6–15.3 kg/mol; Đ = 1.10–1.21) with volume fractions 0.26 ≤ fB ≤ 0.95. A subset of these samples undergo melt self-assembly into cylindrical, lamellar, and apparently bicontinuous morphologies. By assessing the states of order and disorder in these triblock polymer melts using temperature-dependent SAXS, we find that broad B segment Dispersity increases the minimum segregation strength χN ≳ 27 required for LBL triblock self-assembly relative to the self-consistent mean-field theory prediction χN ≥ 17.9 for narrow Dispersity analogues. While B segment Dispersity has previously been shown to thermodynamically stabilize the self-assembled morphologies o...

  • characteristics of lamellar mesophases in strongly segregated broad Dispersity aba triblock copolymers
    Macromolecules, 2014
    Co-Authors: Adam K Schmitt, Mahesh K Mahanthappa
    Abstract:

    We report the synthesis and characterization of a series of 13 strongly segregated poly(lactide-b-1,4-butadiene-b-lactide) (LBL) triblock copolymers, in which a broad Dispersity center B segment (Đ = Mw/Mn ∼ 1.7–1.9) is embedded between two narrow Dispersity L end blocks (Đ ≤ 1.20). Derived from chain transfer ring-opening metathesis polymerization (ROMP-CT) of 1,5,9-cyclododecatriene in the presence of 1,4-diacetoxy-2-butene, α,ω-dihydroxytelechelic poly(1,4-butadienes) serve as ring-opening transesterification polymerization (ROTEP) macroinitiators for the parallel synthesis of LBL triblock copolymers with Mn = 12.4–28.7 kg/mol and volume fractions fB = 0.44–0.79. By determining the Flory–Huggins interaction parameter χLB = 0.192 at 155 °C from mean-field theory analyses of synchrotron X-ray scattering profiles for a narrow Dispersity LB diblock copolymer, we estimate that the segregation strengths associated with the broad Dispersity LBL copolymers range χLBN = 35.1–83.6. As compared to their narrow di...

Yoshimitsu Hamano - One of the best experts on this subject based on the ideXlab platform.

Eric Greve - One of the best experts on this subject based on the ideXlab platform.

  • morphological impact of segment Dispersity in lithium salt doped poly styrene poly ethylene oxide triblock polymers
    Macromolecules, 2019
    Co-Authors: Eric Greve, Mahesh K Mahanthappa
    Abstract:

    We investigate the impact of center segment Dispersity on the phase behavior of 17 lithium salt-doped poly(styrene-block-oligo(ethylene oxide) carbonate-block-styrene) (bSOS) triblock polymers, in which broad Dispersity O blocks (ĐO = Mw/Mn ≈ 1.45) are situated between narrow Dispersity S segments (ĐS ≤ 1.18) with volume fractions fO = 0.33–0.69 and total Mn = 11.6–43.8 kg/mol. Broad Dispersity bSOS triblocks are synthesized by a tandem polycondensation and atom transfer radical polymerization reaction sequence. Using temperature-dependent small-angle X-ray scattering, we map the morphology diagrams for bSOS samples variously doped with lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) with r = (mol Li+)/(mol ethylene oxide) = 0.00–0.09. As compared to the phase behavior exhibited by 13 LiTFSI-doped, narrow Dispersity SOS triblocks with fO = 0.30–0.58 and Mn = 7.1–45.2 kg/mol, we demonstrate that O segment Dispersity shifts the lamellar morphology window to higher fO/salt and the lamellar microdomains di...

  • morphological impact of segment Dispersity in lithium salt doped poly styrene poly ethylene oxide triblock polymers
    Macromolecules, 2019
    Co-Authors: Eric Greve, Mahesh K Mahanthappa
    Abstract:

    We investigate the impact of center segment Dispersity on the phase behavior of 17 lithium salt-doped poly(styrene-block-oligo(ethylene oxide) carbonate-block-styrene) (bSOS) triblock polymers, in ...

Shue Song - One of the best experts on this subject based on the ideXlab platform.

  • preparation and characterization of betamethasone sodium phosphate intercalated layered double hydroxide liposome nanocomposites
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2017
    Co-Authors: Yaping Zhang, Xiaowen Wu, Haiping Li, Na Du, Shue Song
    Abstract:

    Abstract Herein, we report a nanocomposite of betamethasone sodium phosphate (BMP), a glucocorticoid drug, intercalated layered double hydroxide (LDH) nanohybrids encapsulated in liposomes, denoted as BLN@LSs. The BMP-LDH nanohybrids (BLNs) were firstsynthesized via a coassembly route between BMP anions and LDH single-layer nanosheets (SLNSs), and then coated with liposomes consisting of lecithin and cholesterol. The re-Dispersity, stability, and drug release behavior of the so-obtained nanocomposites were investigated. Compared with BLNs, the BLN@LSs exhibit excellent water re-Dispersity and stability as well as enhanced drug sustained-release performance. The drug release processes can be described using the pseudo-second-order kinetic model, and intraparticle diffusion is the release rate-limiting step. Our work demonstrates that liposome-coating for drug-LDH nanohybrids is an effective strategy to enhance their water Dispersity and sustained-release performances, and that (drug-LDH)@LS nanocomposites are a potential drug delivery system.

  • preparation and characterization of betamethasone sodium phosphate intercalated layered double hydroxide liposome nanocomposites a physicochemical and engineering aspects
    Colloids and Surfaces, 2017
    Co-Authors: Yaping Zhang, Xiaowen Wu, Haiping Li, Na Du, Shue Song
    Abstract:

    Herein, we report a nanocomposite of betamethasone sodium phosphate (BMP), a glucocorticoid drug, intercalated layered double hydroxide (LDH) nanohybrids encapsulated in liposomes, denoted as BLN@LSs. The BMP-LDH nanohybrids (BLNs) were firstsynthesized via a coassembly route between BMP anions and LDH single-layer nanosheets (SLNSs), and then coated with liposomes consisting of lecithin and cholesterol. The re-Dispersity, stability, and drug release behavior of the so-obtained nanocomposites were investigated. Compared with BLNs, the BLN@LSs exhibit excellent water re-Dispersity and stability as well as enhanced drug sustained-release performance. The drug release processes can be described using the pseudo-second-order kinetic model, and intraparticle diffusion is the release rate-limiting step. Our work demonstrates that liposome-coating for drug-LDH nanohybrids is an effective strategy to enhance their water Dispersity and sustained-release performances, and that (drug-LDH)@LS nanocomposites are a potential drug delivery system.

Chitose Maruyama - One of the best experts on this subject based on the ideXlab platform.