Cotton Fibers Encapsulated with Homo- and Block Copolymers:  Synthesis by the Atom Transfer Radical Polymerization Grafting-From Technique and Solid-State NMR Dynamic Investigations

Abstract

Cotton fibers were modified by surface-initiated atom transfer radical polymerization of ethyl acrylate (EA) followed by copolymerization with styrene. Either ethyl 2-bromopropionate as a sacrificial free initiator or Cu(II) as a deactivator was used to optimize the EA grafting yield and to preserve the livingness of the chain ends for the subsequent growth of a poly(styrene) (PSty) block from the poly(ethyl acrylate) (PEA) grafts. The polymer-encapsulated cotton fibers were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and solid-state NMR (high-resolution 13C cross-polarization magic angle spinning, 1H spin-lattice relaxation times, and 1H free induction decay analysis NMR). The latter allowed the detection of the dynamic modifications associated with the presence of homo- and block copolymer grafts. In particular, the results of the DSC and NMR investigations suggest a heterogeneous morphology of the g-PEA-b-PSty grafted skin, which could be described as an inner layer of g-PEA sandwiched between the semicrystalline cellulose of the core fiber and the high glass transition temperature PSty of the covalently linked outer layer. Such morphology results in a reduced molecular mobility of the PEA chains.

Grafting from ramie fiber with poly(MMA) or poly(MA) via reversible addition-fragmentation chain transfer polymerization

“…Moreover, due to the basic property of NMP, it can be used as a proton scavenger to form a stable salt in the system. Also NMP is a good solvent for the catalyst and BIBB used, so the esterification reaction can proceed more efficiently, which simplified the step compared with the previous reported literature (Roy et al 2005;Daly et al 2001;Carlmark and Malmström 2002;Plackett et al 2005;Castelvetro et al 2007). A large excess of BIBB was required in this reaction system to improve the reaction efficiency and obtain an enough high degree of substitution and a detectable grafting yield in the following grafting polymerization step, that is, one has a capability of converting the ramie fiber into efficient RAFT initiating sites for the subsequent grafting copolymerization.…”

“…Moreover, to demonstrate the ''living'' character of ATRP technique, they successfully grafted a second hydrophilic polymer, poly (2-hydroxyethyl methacrylate; PHE-MA), upon the PMA layer (Carlmark and Malmström 2003). In addition, Plackett et al (2005) and Castelvetro et al (2007) used jute fibers and cotton fibers as a natural cellulose resource to prepare functional composite cellulose-based materials via similar surfaceinitiated ATRP methods, respectively. With respect to these methods, however, their disadvantages cannot be ignored, such as high reaction temperatures and few available monomers in the case of NMP and contamination problem due to the residues of catalyst and ligand in the case of ATRP.…”

Protein Immobilization onto Poly(acrylic acid) Functional Macroporous PolyHIPE Obtained by Surface-Initiated ARGET ATRP

“…32 Moreover, it is a convenient indirect reporter for the molecular weight and polydispersity (PDI) of the surfaces grafted polymers provided there is a good correlation between the polymer growth from the surface and in solution. 33,34,35,36,37 In our case the sacrificial initiator EBiB is a α-halogen ester whereas the surface initiator is an amide. The latter have been reported to be prone to a higher termination rate in the initial phase of conventional ATRP resulting in higher PDIs and molecular weighs.…”

Developments in Solid-State NMR Spectroscopy of Polymer Systems

“…The graft copolymer-encapsulated cotton fibers were studied by 1 H T 1 relaxation experiments, yielding the observation of a heterogeneous morphology of the grafted skin [30].…”