Glasses‐shaped triblock copolymer prepared by combination of atom transfer radical polymerization and ring opening polymerization

Abstract

A glasses-shaped triblock copolymer of poly(ε-caprolactone)-b-polystyrene-bpoly(ε-caprolactone) (PCL-b-PS-b-PCL) is prepared by combining atom transfer radical polymerization (ATRP) and ring opening polymerization (ROP).Polystyrene (PS) star polymers are prepared via ATRP using a tetra-functional initiator, followed by azidation to yield azide end-functionalized star polymers. An alkyne-functionalized coupling agent, 2,2-bis[(2-propyn-1-yloxy)methyl]-1-propanol is employed to produce hydroxy 8-shaped PS via copper(I)catalyzed alkyne-azide cycloaddition. Herein, hydroxy 8-shaped PS with high purity is obtained through preparative size exclusion chromatography (Prep SEC) and high-performance liquid chromatography, followed by the characterizations using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), size exclusion chromatography (SEC), infrared, and proton nuclear magnetic resonance ( 1 H NMR) spectroscopy. The hydroxy groups of the 8-shaped PS are utilized as initiators for the ROP of ε-caprolactone to obtain linear chains attached to the 8-shaped architecture.After SEC fractionation, the glasses-shaped triblock copolymer is characterized using 1 H NMR and SEC. This unprecedented topology possesses two free chain-ends and two cycles; thus, both the properties of linear and cyclic polymers may be expected to be observed.

Low-Pressure Preparative Size-Exclusion Chromatography: from Narrow Disperse Polymer to Monodisperse Oligomer Batches

“…In addition to the preparation, effective protocols are required, e.g., to narrow the previously prepared crude polymer’s dispersity ( Đ ), to fractionate according to molar mass ( M n ), and/or to isolate discrete oligomer batches ( n ). For the latter, adsorption chromatography on normal- and/or reversed stationary phases can be used in HPLC- , and flash chromatography-based fractionation protocols. − However, the chromatographic conditions must be specifically optimized for each polymer type. In contrast, the size-exclusion chromatography (SEC) approach appears more universal but needs to be adapted to a preparative scale as well as the desired molar mass range.…”

“…For the latter, adsorption chromatography on normal-and/or reversed stationary phases can be used in HPLC- 32,33 and flash chromatography-based fractionation protocols. 34−40 However, the chromatographic conditions must be specifically optimized for each polymer type.…”

“…Such specialized high-pressure recycling SEC (HP-rSEC) systems were utilized for the isolation of various oligomer types, e.g., side-chain oligo(fluorene)s, 16 conjugated oligo(octithienyl-diethynyl)s, 17 oligo(acrylate)s, 41 or conjugated oligo(fluorene)s 15 �as well as to sharpen polymer distributions 42 or to obtain precise macromolecular architectures. 33 Notably, peak broadening upon passage of the pump head and injector unit arises from their dead volumes. As a consequence, specialized pump head or valve configurations become necessary, 43 which renders this methodology costly and limited to a number of laboratories.…”

“…In the case of the latter, a recycling valve can be included that redirects the eluted material back to the pump inlet, which effectively elongates the net bed volume by each performed cycle ( vide infra ). Such specialized high-pressure recycling SEC (HP-rSEC) systems were utilized for the isolation of various oligomer types, e.g., side-chain oligo­(fluorene)­s, conjugated oligo­(octithienyl-diethynyl)­s, oligo­(acrylate)­s, or conjugated oligo­(fluorene)­sas well as to sharpen polymer distributions or to obtain precise macromolecular architectures . Notably, peak broadening upon passage of the pump head and injector unit arises from their dead volumes.…”