(75) ACS Catal. 2025, 15, 9, 7588–7600
Synthesizing a pure, high molecular weight block copolymer of methyl methacrylate (MMA) and lactide (LA) using a one-pot, sequential addition approach is challenging, as these two monomers are generally polymerized via orthogonal mechanisms. In this work, we report the synthesis of PMMA-b-PLA using a cationic indium complex featuring a hemilabile arm. Extensive efforts were made to confirm block copolymer formation, differentiate it from homopolymer blends, and quantify homopolymer impurities….
(74) ACS Macro Lett. 2024, 13, 2, 266–272
“Synthesis of High-Molecular-Weight Poly(ether-alt-ester) by Selective Double Ring-Opening Polymerization of Spiroorthoesters”
We report the selective double ring-opening polymerization of presequenced spiroorthoester monomers to form high-molecular-weight (≈90 kDa) poly(ether-alt-ester)s with a simple cationic alkyl gallium catalyst. The selective formation of double ring-opened polymer units was confirmed by NMR and IR spectroscopies. Thermal and rheological properties of homo- and copolymers were further characterized by differential scanning calorimetry, thermogravimetric analysis, and stress-controlled rotational rheometry….
(73) Dalton Trans., 2024, 53, 19337–19341
“Alkyl initiated ring opening polymerization of lactide by indium complexes supported by NCN pincer ligands”
Indium-alkyl NCN pincer complexes supported by amine and imine donors are active catalysts for the ring opening polymerization of lactide. The amine indium complexes are significantly more active for polymerization due to the decoordination of the amine donors at higher temperatures. Solid state structures of the imine and amine indium complexes indicate that the imine–indium bonds are stronger than the analogous amine–indium bonds….
(72) RSC Sustain., 2024, 2, 1543–1550
“Cellulose nanocrystal-mediated enhancement of hydrogel anti-swelling and water retention”
Research into the creation of flexible electronics has expanded because of the growing interest in wearable electronic devices. The field of iontronics employs ionic conductive hydrogels (IHCs) to access flexible devices that utilize ions as charge carriers. Hydrogel ionic conductors suffer from drawbacks such as low conductivity, water evaporation, over-swelling, and weak mechanical properties. Hydrogels are prone to swelling in aqueous environments; however, excessive swelling is undesirable for water-based applications since overswelling adversely affects the mechanical properties….
(71) ACS Catal. 2023, 13, 20, 13195–13204
“Mechanistic Insights into Selective Indium-Catalyzed Coupling of Epoxides and Lactones”
Spiro-orthoesters, produced from the coupling of lactones and epoxides, are presequenced monomers capable of generating alternating poly(ether-alt-esters) after ring-opening polymerization. Recently, we reported the selective synthesis of spiro-orthoesters through the coupling of epoxides and lactones catalyzed by a cationic alkyl indium catalyst. Herein, we investigate the mechanism of this reaction using structure–function relationships and computational studies. We show that this reaction is governed by Michaelis–Menten-type saturation kinetics, which, along with the low Lewis acidity of these indium catalysts, explains their selectivity….
(70) Carbohydr. Polym., 2023, 302, 120378
“Impact of counterion valency on the rheology of sulfonated cellulose nanocrystal hydrogels”
A systematic rheological study on the influence of valency of different counterions on the properties of CNC hydrogels was carried out. Rheo-polarized microscopy was used to prove that preshear of 500 s−1 for 1 min is adequate to completely breakdown agglomerates in the suspension. Furthermore, a rest period of 30 min is sufficient to recover the equilibrium structure of hydrogels. Changing counterions from monovalent (Na+, K+, Li+), to divalent (Mg2+, Ca2+) and to trivalent (Al3+) influenced the network formation….
(69) RSC Sustain., 2023, 1, 1369–1385
” Utilizing cellulose-based conducting hydrogels in iontronics”
The rising interest in wearable devices has galvanized research into the development of flexible electronics. Flexible iontronics, devices that employ ions as charge carriers, have been accessed by employing ionic conductive hydrogels. While petroleum-based polymers have dominated this field, recently there is a drive towards renewable alternatives to develop more sustainable alternatives. This review focuses on the use of cellulose in ionic conductive hydrogels (IHCs) and their application in fabricating iontronics….
(68) Inorg. Chem. 2023, 62, 5, 1968–1977
“Cooperative Initiation in a Dinuclear Indium Complex for CO2 Epoxide Copolymerization”
Dinuclear indium complexes have been synthesized and characterized. These include neutral and cationic indium complexes supported by a Schiff base ligand bearing a binaphthol linker. The new compounds were investigated for alternating copolymerization of CO2 and cyclohexene oxide. In particular, the neutral indium chloride complex (±)-[(ONapNiN)InCl2]2 (4) showed high conversion of cyclohexene oxide and selectivity for poly(cyclohexene carbonate) formation without cocatalysts at 80 °C under various CO2 pressures (2–30 bar)….
(67) ACS Catal. 2023, 13, 24, 16148–16157
“Rethinking the Lewis Acidity of Cationic Gallium and Indium Catalysts”
Indium compounds are commonly considered weaker Lewis acids than their gallium counterparts. We explore the difference in Lewis acidity of the cationic dialkylgallium [GaR2(THF)2]+ and indium [InR2(THF)n]+ species and show that the gallium compounds are more active for the cationic polymerization of epoxide and ε-caprolactone. We rationalize this difference in reactivity by quantifying the relative Lewis acidity of the gallium and indium complexes….
(66) ACS Sustainable Chem. Eng. 2022, 10, 8, 2772–2783
“Poly(Lactide)-Modified Lignin Nanofibers: Investigating the Role of Polymer Tacticity on Fiber Properties and Filtration Efficiency”
Lignin-graft-PLLA and lignin-graft-PDLA copolymers were synthesized and transformed into nanofibers through electrospinning. The nanofibers generated with either lignin-graft-PLLA or lignin-graft-PDLA showed X-ray diffraction (XRD) patterns corresponding to the homocrystallites of isotactic poly(lactic acid) (PLA), whereas the nanofibers generated with 1:1 v/v solution blend of lignin-graft-PLLA/lignin-graft-PDLA showed stereocomplexation of the PLA chains….
(65) Chem. Commun., 2022, 58, 6192–6195
“Thermally stable zinc hydride catalyst for hydrosilylation of CO2 to silyl formate at atmospheric pressure”
Neutral zinc complexes supported by H[PNNO], a diaminophenolate ligand bearing a pendant phosphine group, were synthesized and characterized. The phosphine arm adopts two different configurations in solution and prevents aggregation. The monomeric zinc hydride complex is stable at elevated temperatures up to 125 °C and reacts readily with CO2 to afford a zinc formate complex. The zinc hydride is active for CO2 hydrosilylation at atmospheric CO2 pressure and is selective for CO2 reduction to the silyl-formate product…
(64) Inorg. Chem., 2022, 61, 8, 3763–3773
“Comparison of Imine- and Phosphinimine-Supported Indium Complexes: Tuning the Reactivity for the Sequential and Simultaneous Copolymerization of Lactide and ε-Caprolactone”
Imine- and phosphinimine-supported indium complexes were used as catalysts in the polymerization of racemic lactide and ε-caprolactone as well as their copolymerization by the sequential and simultaneous addition of monomers. Tuning the electronics and sterics of the indium centers by either (i) changing the nature of the nitrogen donors and (ii) coordinating a hemilabile side group had a significant effect on the reactivity of the complexes, their stability, and their control in the synthesis of block copolymers….
(63) Chem. Sci., 2022, 13, 3713–3718
“Temperature triggered alternating copolymerization of epoxides and lactones via pre-sequenced spiroorthoester intermediates”
We report the alternating copolymerization of caprolactone and epoxide through the in situ formation of pre-sequenced spiroorthoester monomer. The reaction is catalyzed by the temperature triggered, bifunctional cationic indium complex (±)-[(NNiOtBu)In(CH2SiMe3)][B(C6F5)4]….
(62) ACS Catal. 2022, 12, 13, 7677–7686
“An Air Stable Cationic Indium Catalyst for Formation of High-Molecular-Weight Cyclic Poly(lactic acid)”
Overcoming entropic constraints to selectively produce high-molecular-weight cyclic poly(lactide) (c-PLA) is a challenge. In this work, we use an air-stable cationic alkyl indium complex featuring a hemilabile pyridine pedant arm to reproducibly synthesize c-PLA exclusively with low dispersity (Đ ∼ 1.30) and high molecular weights (up to 416,000 g mol–1)….
(61) Inorg. Chem. 2021, 60, 24, 19304–19314
“Indium-Catalyzed CO2/Epoxide Copolymerization: Enhancing Reactivity with a Hemilabile Phosphine Donor”
Group 13 metal complexes have emerged as powerful catalysts for transforming CO2 into added-value products. However, direct comparisons of reactivity between Al, Ga, and In catalysts are rare. We report aluminum , gallium , and indium complexes supported by a half-salen H[PNNO] ligand with a pendent phosphine donor and investigate their activity as catalysts for the copolymerization of CO2 and cyclohexene oxide…
(60) Catal. Sci. Technol.2021, 11, 62–91
“Cationic aluminum, gallium, and indium complexes in catalysis”
“Cationic and Anionic Cellulose Nanocrystalline (CNC) Hydrogels: A Rheological Study ”
Although the rheology of cellulose nanocrystalline (CNC) suspensions has been widely studied, less attention has been paid to the modified cellulose nanocrystals such as cationic and anionic cellulose hydrogels. In this work, the rheological behavior of cellulose nanocrystals (CNCs), anionic CNCs (pCNCs), and cationic CNCs (nCNCs), was comparatively studied. …
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(58) Phys. Fluids 2021, 33, 032010
“The rectification mechanism in polyelectrolyte gel diodes ”
Ionic driven devices have been increasingly investigated in the drive to develop flexible and biointegrable electronics. One such device is a polyelectrolyte gel diode capable of rectifying ionic current. However, the underlying mechanism behind the rectification of current in polyelectrolyte gel diodes is not fully understood. Based on experimental data, it has been proposed that the rectification is due to theasymmetric distribution …
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(57) Polym. Chem. 2021, 12, 783 – 806
“Strategies for the Synthesis of Block Copolymers with Bio-Based Components”
The controlled synthesis of block copolymers offers great potential for the valorization of biodegradable polyesters, many of which can be bioderived. Combining polyester blocks with other oxygenated polymers through ring-opening polymerization (ROP) and copolymerization (ROCOP) reactions allows for the synthesis of new materials with tunable properties. In this review article, we describe recent advances in the synthesis of diblock and multiblock polyesters, as well as …
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(56) Catal. Sci. Technol. 2021, 11, 2119–2129
“Conversion of Dilute CO2 to Cyclic Carbonates at Sub-atmospheric Pressures by a Simple Indium Catalyst”
The transformation of CO2 to value added commodity chemicals presents an impactful strategy to obtain products that are less dependent on fossil fuels. In this study, indium tribromide (InBr3) mixed with tetrabutylammonium bromide (NBu4Br) co-catalyst has been identified as a simple, highly efficient catalyst for the synthesis of cyclic carbonates from epoxides and CO2 at sub-atmospheric pressures, room temperature …
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(55) Catal. Sci. Technol. 2020 11, 62-91
“Cationic Aluminum, Gallium, and Indium Complexes in Catalysis”
Neutral heavier group 13 metals aluminum, gallium, and indium have been utilized as Lewis acid catalysts in various organic transformations ranging from classical organic reactions to polymerization reactions. The introduction of cationic charge can enhance the Lewis acidity of metal centers and allow cationic group 13 complexes to be excellent catalysts in Lewis acid catalysis, ….
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(54) ACS Appl. Mater. Interfaces 2020, 12, 52182−52191
“Toward Biodegradable electronics: Ionic diode based on a cellulose nanocrystals-agarose hydrogel”
Bioderived cellulose nanocrystals (CNCs) are used to create light, flexible, biocompatible, and biodegradable electronic devices. Herein, surface modification of cellulose nanocrystals was
employed to fabricate cationic and anionic CNCs. Subsequently, we demonstrated rectification behavior from a fixed junction between two agarose hydrogels doped with cationic and anionic cellulose nanocrystals….
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(53) Macromolecules 2020, 53(20), 8819-8828
“One-pot Synthesis of Oxygenated Block Copolymers by Polymerization of Epoxides and Lactide Using Cationic Indium Complexes”
Cationic indium complexes were used as catalysts for the copolymerization of epoxides and racemic lactide (rac-LA) via sequential addition to form high molecular weight block copolymers. Mechanistic studies and control experiments indicate that the epoxide is polymerized by a cationic mechanism to yield a neutral alkoxide indium species that subsequently polymerizes the lactide ….
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(52) ACS Catal. 2020, 10, 6488−6496
“Indium-catalyzed block copolymerization of lactide and methyl methacrylate by sequential addition”
We report a metal-mediated sequential addition synthetic route for copolymerization of lactide (or e-caprolactone) and methyl methacrylate. We synthesized a series of neutral and cationic indium complexes supported by tridentate Schiff base ligands and investigated their reactivities for the homo- and copolymerization of lactide or e-caprolactone and methyl methacrylate. ….
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(51) Chem. Sci. 2020, 11, 6485−6491
“Cationic indium catalysts for ring opening polymerization: Tuning reactivity with hemilabile ligands”
This is a comprehensive study of the effects of rationally designed hemilabile ligands on the stability, reactivity, and change in catalytic behavior of indium complexes. We report cationic alkyl indium complexes supported by a family of hemi-salen type ligands bearing hemilabile thiophenyl (2a), furfuryl (2b) and pyridyl (2c) pendant donor arms. Shelf-life and stability of these complexes ….
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(50) Inorg. Chem. 2020, 59, 5546−5557
“Dinucleating Amino-Phenolate Platform for Zinc Catalysts: Impact on Lactide Polymerization”
We report imine and amine-based dinucleating ligands bearing a bisphenol backbone and explore their coordination chemistry with zinc complexes to form zinc alkyl, alkoxide, acetate, and amide complexes. Full characterization of the complexes shows that this ligand framework can support dinuclear and trinuclear complexes. We explore the reactivity of the zinc alkyl and alkoxide ….
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(49) Chem. Commun. 2019, 55, 3347-3350
“Cationic indium complexes for the copolymerization of functionalized epoxides with cyclic ethers and lactide”
We report the first example of discrete cationic indium complexes for the copolymerization of epoxides, cyclic ethers, and lactide. [SalenIn][SbF6] in particular proved to be a highly active catalyst for the homo-polymerization of functionalized epoxides and their copolymerization with other cyclic ethers THF, oxetane and oxepane. ….
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(48) Coord. Chem. Rev. 2019 380, 35–57
“Dinuclear catalysts for the ring opening polymerization of lactide”
Discrete metal initiators are comprised of an electropositive metal center, an ancillary ligand, and an initiating group such as an amide or an alkoxide. This difference in polarity between the electrophilic metal centers and the nucleophlic initiators often leads to catalyst aggregation. Partially due to this phenomenon, bimetallic catalysts, either dimeric, tethered, or dinucleating, are gaining attention as catalysts ….
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(47) ChemCatChem 2018, 10, 3219 – 3222
“Coupling of Epoxides and Lactones by Cationic Indium Catalysts To Form Functionalized Spiro-Orthoesters”
We prepared a cationic indium catalyst for the conversion of epoxides and lactones into spiro-orthoesters (SOEs), a family of expanding monomers. The cationic indium alkyl complexes were synthesized and fully characterized. The reaction of e-caprolactone with 1,2-epoxy-7-octene resulted in the formation of 2-(hex-5-en-1-yl)-1,4,6-trioxaspiro[4.6]undecane (SOE1) with full conversion of both components ….
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(46) ACS Sustainable Chem. Eng., 2018, 6, 1650–1661
“Synthesis and thermorheological analysis of biobased lignin-graft-poly(lactide) copolymers and their blends”
Despite numerous accounts of biobased composite materials through blending and copolymerization of lignin and other polymers, there are no systematic studies connecting the synthetic methodology, molecular structure, and polymer topology with ….
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(45) Acc. Chem. Res. 2017, 50, 2861−2869
“Indium catalysts for ring opening polymerization: Exploring the importance of catalyst aggregation”
Inexorably, the environmental persistence and damage caused by polyolefins have become major drawbacks to their continued long-term use. Global shifts in thinking from fossil-fuel to renewable biobased resources have urged researchers to focus their attention ….
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(44) J. Rheol. 2017, 61(6), 1137-1148
“Aromatic interactions in aryl-capped polylactides: A thermorheological investigation”
A series of aryl-capped poly(lactide)s (PLAs) were synthesized by living ring-opening polymerization with a chain transfer agent (also referred to as immortal polymerization, iROP) using a previously reported dinuclear indium catalyst, [(NNO)InCl]2(μ-Cl)(μ-OEt) (A) ….
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(43) ACS Catal. 2017 7, 6413–6418
“Air- and Moisture Stable Indium Salan Catalysts for Living Multiblock PLA Formation in Air”
We introduce an air- and moisture-stable hydroxy-bridged indium salan complex as a highly active and controlled catalyst for the ring- opening polymerization of cyclic esters in air. The reversible activation of this complex with linear and branched alcohols ….
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(42) Dalton Trans. 2017 46, 6723–6733
“Impact of Aryloxy Initiators on the Living and Immortal Polymerization of lactide”
This report describes two different methodologies for the synthesis of aryl end-functionalized poly (lactide)s (PLAs) catalyzed by indium complexes. In the first method, a series of para-functionalized phenoxy-bridged dinuclear indium complexes …
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(41) Macromolecules 2017 50 (6), 2535–2546
“Binary Blends of Entangled Star and Linear poly(hydroxybutyrate): Effect of Constraint Release and Dynamic Tube Dilation”
In order to further understand the relaxation behavior of binary blends of star and linear chains, new polymer blends consisting of linear poly(hydroxybutyrate) (PHB) matrix and PHB star molecules are designed, and their dynamics is investigated by varying the star concentrations …
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(40) Inorg. Chem. 2017 56 (3), 1375–1385
“A Comparison of Gallium and Indium Alkoxide Complexes as Catalysts for Ring-Opening Polymerization of Lactide”
The impact of the metal size and Lewis acidity on the polymerization activity of group 13 metal complexes was studied, and it was shown that, within the same ligand family, indium complexes are far more reactive and selective than their gallium analogues. To this end …
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(39) Macromolecules 2016 49 (23), 8812–8824
“Highly Active Chiral Zinc Catalysts for Immortal Polymerization of β‐Butyrolactone Form Melt Processable Syndio-Rich Poly(hydroxybutyrate)”
Highly crystalline poly(hydroxybutyrate) suffers from high melting point and entanglement molecular weight. This leads to low melt strength, limits processing through regular techniques, and precludes many applications. In this work we report a series of racemic …
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(38) Inorg. Chem. 2016, 55(18), 9445–9453
“The role of nitrogen donors in zinc catalysts for lactide ring opening polymerization”
The electronic effects of nitrogen donors in zinc catalysts for ring opening polymerization of cyclic esters were investigated. Alkyl and benzyloxy zinc complexes supported by tridentate diamino- and aminoimino phenolate ligands were synthesized and their …
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(37) Inorg. Chem. 2016, 55(11), 5365–5374
“Dinucleating ligand platforms supporting indium and zinc catalysts for cyclic ester polymerization”
The synthesis of the first alkoxide-bridged indium complex supported by a chiral dinucleating ligand platform (1), along with its zinc analogue (2), is reported. Both complexes are synthesized in a one-pot reaction starting from a chiral dinucleating …
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(36) Macromolecules 2016, 49(3), 909–919
“A comparison of the rheological and mechanical properties of isotactic, syndiotactic, and heterotactic PLA”
A series of poly(lactide) (PLA) samples, exhibiting various levels of syndiotactic enrichment, were formed via the ring-opening polymerization of meso-lactide using two families of novel dinuclear indium catalysts…
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(35) Macromolecules 2015, 48 (18), 6672–6681
“Synthesis and Rheological Characterization of Star-Shaped and Linear Poly(hydroxybutyrate)”
Indium and zinc complexes, [(NNOtBu)InCl]2(μ-Cl)(μ-OTHMB) (2) and (NNiOtBu)Zn(CH2CH3) (3), were used to produce monodispersed three- and six-armed star-shaped PHBs using tris(hydroxymethyl)benzene (THMB) and…
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(34) Chem. Sci., 2015, 6, 5284–5292
“Overcoming aggregation in indium salen catalysts for isoselective lactide polymerization.”
A methodology for controlling aggregation in highly active and isoselective indium catalysts for the ring opening polymerization of racemic lactide is reported. A series of racemic and enantiopure dinuclear…
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(33) Dalton Trans. 2015, 44, 14248 – 14254
“Star-shaped PHB-PLA block copolymers: Immortal polymerization with dinuclear indium catalysts”
The first example of a one-component precursor to star-shaped polyesters, and its utilization in the syn- thesis of previously unknown star-shaped poly(hydroxybutyrate)–poly(lactic acid) block copolymers,…
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(32) Dalton Trans. 2015, 44, 6126 – 6139
“Effect of steric changes on the isoselectivity of dinuclear indium catalysts for lactide polymerization”
Functionalized diaminophenolates as ligands for dinuclear indium catalysts were investigated in the ring-opening polymerization of lactide. An increase in the steric bulk of the ligand…
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(31) Inorg. Chem. 2014, 53(18), 9897−9906
“Probing the role of secondary vs. tertiary amine donor ligands for indium catalysts in lactide polymerization”
The role of the central amine donor in a previously reported dinuclear indium catalyst, [NMe2NHO)InCl]2(m-Cl)(m-OEt) (1), for the polymerization of lactide was investigated through…
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(30) J. Am. Chem. Soc. 2014, 136(32), 11264–11267
“Redox Control of Group 4 Metal Ring-Opening Polymerization Activity toward l-Lactide and ε-Caprolactone”
The activity of several group 4 metal alkoxide complexes supported by ferrocene-based ligands was controlled using redox reagents during the ring-opening polymerization of l-lactide and…
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(29) Inorg. Chem. 2014, 53(13), 6828–6836
“The role of aggregation in the synthesis and polymerization activity of SalBinap indium alkoxide complexes”
The reaction of racemic SalBinap ligand, (±)-H2(ONN*OMe) with InCl3 and excess NaOEt generated a mixture of two dinuclear compounds [(µ-κ2-ONN*OMe)In(µ-OEt)]2 (1a) and [κ4-ONN*OMe)In(µ-OEt)]2…
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(28) Organometallics 2013, 32(23), 6950–6956
“Theoretical Investigation of Lactide Ring-Opening Polymerization Induced by a Dinuclear Indium Catalyst”
A DFT study of the ring-opening polymerization of lactide (LA) induced by a dinuclear indium catalyst supported by a chiral diamino phenoxy ligand, [(NNHO)InCl]2(μ-Cl)(μ-OEt) (1), is reported….
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(27) Macromolecules 2013, 46, 3965−3974
“PLA-PHB-PLA triblock copolymers: Synthesis by sequential addition and investigation of mechanical and rheological properties”
The dinuclear indium catalyst [(NNO)InCl]2(μ-OEt)(μ-Cl), previously reported to be highly active for the living ring-opening polymerization of cyclic esters lactide (LA) and…
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(26) Chem. Commun. 2013, 49, 4295-4297
“A highly active and site selective indium catalyst for lactide polymerization”
Invited article in the “Emerging Investigators” issue.
Chiral indium salen complexes are highly active, isoselective catalysts for the ring opening polymerization of racemic lactide. The polymerizations are well controlled…
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