Synthesis and characterization of temperature‐sensitive block copolymers from poly(N‐isopropylacrylamide) and 4‐methyl‐ε‐caprolactone or 4‐phenyl‐ε‐caprolactone

Abstract

This study synthesizes thermally sensitive block copolymers poly(N-isopropylacrylamide)-b-poly(4-methyl-e-caprolactone) (PNIPA-b-PMCL) and poly(N-isopropylacrylamide)-b-poly(4-phenyl-e-caprolactone) (PNIPAb-PBCL) by ring-opening polymerization of 4-methyl-e-caprolactone (MCL) or 4-phenyl-e-caprolactone (BCL) initiated from hydroxy-terminated poly(N-isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct 2 as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2-hydroxyethanethiol (ME) as a chain-transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), 1 H-NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (T g ) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases T g . Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA-b-PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29-2.74 mg L À1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions.

Strong, Resilient, and Sustainable Aliphatic Polyester Thermoplastic Elastomers

“…Moreover, the polymerization of γ-methyl-ε-caprolactone (γMCL) is known to be faster than γ-substituted ε-caprolactones with longer alkyl chains (ethyl, butyl, and propyl substituents) . The low glass transition temperature of PγMCL ( T g = −61 °C) has motivated the use of this polymer in biomedical applications. − Combined, these attributes make PγMCL an interesting and desirable polymer to incorporate into PLA-TPEs. Moreover, γMCL can be synthesized through the Baeyer–Villiger oxidation of 4-methylcyclohexanone, a molecule that can ultimately be sourced from cresols.…”

Efficient Polymerization of Methyl-ε-Caprolactone Mixtures To Access Sustainable Aliphatic Polyesters

“…Ring-opening polymerization (ROP) of lactones has proven instrumental in the synthesis of sustainable aliphatic polyesters with attractive and competitive material properties when compared to petrochemically derived analogues. The uses for these polymers include tough thermoplastic elastomers, polyurethane foams, thermosets, elastomers, and block copolymer-based micelles. − Given their versatility, there is a need to better understand how next-generation aliphatic polyesters are sourced and manufactured. Poly­(γ-methyl-ε-caprolactone) (PγMCL) has been employed for many of these applications due in large part to favorable polymerization kinetics and thermodynamics via metal-catalyzed ROP of γ-methyl-ε-caprolactone (γMCL), a low entanglement molar mass ( M e ), and potential biodegradability. , Moreover, several researchers have invoked facile retrosynthetic routes that would enable access to γMCL, among other valuable molecules, from sustainable biomass-derived feedstocks. − In particular, lignin represents an enticing starting material due to its abundant supply and a surfeit of sources that generate it as a by-product of industrial scale processes, such as paper pulp refining and the lignocellulose-to-ethanol process. , Lignin bio-oils are the depolymerization products of lignins and are complex mixtures, comprised of hundreds of phenolic and cyclic aromatic compounds, the composition of which varies widely depending on such factors as lignin feedstock type, depolymerization method, heating rate, reaction temperature, and catalysts .…”

Synthesis, Self-Assembly, and Drug Delivery Characteristics of Poly(methyl caprolactone-co-caprolactone)-b-poly(ethylene oxide) Copolymers with Variable Compositions of Hydrophobic Blocks: Combining Chemistry and Microfluidic Processing for Polymeric Nanomedicines

“…Poly­(4-methyl-ε-caprolactone) and poly­(6-methyl-ε-caprolactone) (PMCL) are hydrophobic polymers that are structurally similar to PCL but with a methyl group on each repeat unit that disrupts the ability of the chains to close-pack. , Therefore, in contrast to PCL, both PMCL isomers are amorphous, low- T g polymers. − The synthesis, properties, self-assembly, and drug delivery applications of amphiphilic block copolymers based on PMCL hydrophobic blocks have been described by several groups. − In addition, Wang et al reported the copolymerization of 4-methyl-ε-caprolactone (MCL) and ε-caprolactone (CL) to generate hydrophobic P­(MCL- co -CL) random copolymers with various ratios of MCL and CL monomers; characterization of their physical and biomedical properties (including degradability and biocompatibility) suggested that such copolymers with variable MCL contents could offer interesting and variable properties for biomedical applications, including drug delivery . However, to induce amphiphilic self-assembly, hydrophobic random copolymers of this type would need to be joined to a hydrophilic polymer block such as PEO.…”