Query: ATRP,  metal- free，cellulose

title: Integration of metal free ATRP and Diels Alder reaction toward sustainable and recyclable cellulose based thermoset elastomers.
abstract: Well defined sustainable and recyclable thermoset elastomers derived from cellulose, fatty acid and furfural were successfully prepared via photoinduced metal free ATRP and Diels Alder (DA) reaction. Firstly, metal free ATRP was applied to prepare a range of thermoplastic cellulose graft copolymers with furfural groups. Then, a modified epoxidized soybean oil bearing 6 maleimidohexanoic group (ESOM) as a crosslinker was employed to perform DA reaction with furfural groups in these cellulose graft copolymers, by which the copolymer formed the dynamic crosslinked network and achieved the thermoset elastomers. The dynamic crosslinked network formed by DA reaction not only could increase the chain entanglement that was associated with the improved flexibility and could contribute to enhancing the mechanical strength up to 166 but also endowed these thermoset elastomers with recyclability, excellent shape memory and self healing property. These thermoset elastomers can be used as self healing strain sensor and wearable sensing devices after compounding them with carbon nanotubes.

title: Metal free ATRP "grafting from" technique for renewable cellulose graft copolymers
abstract: Photoinduced metal free "grafting from" atom transfer radical polymerization (ATRP) has been successfully applied to the fabrication of renewable cellulose graft copolymers with the aid of 2 bromo 2 phenylacetyl ester modified ethyl cellulose as the macroinitiator. In the presence of an organic based photoredox catalyst, "grafting from" polymerization of lauryl methacrylate from ethyl cellulose was efficiently activated and deactivated with UV irradiation, resulting in good control over molecular weight. 1H NMR and MALDI TOF MS confirmed highly preserved Br chain end functionality. Furthermore, cellulose graft copolymers with a block side chain architecture were successfully prepared through chain extension by metal free "grafting from" ATRP. We believe that this work will provide a novel approach to design well defined cellulose graft copolymers and further expand their application fields.

title: Pickering emulsion of metal free photoinduced electron transfer ATRP stabilized by cellulose nanocrystals
abstract: The development of metal free photoinduced electron transfer atom transfer radical polymerization (PET ATRP) in Pickering emulsion by cellulose nanocrystals (CNCs) has successfully investigated. In the presence of ethyl 2 bromoisobutyrate (initiator) and triethylamine (additives) Eosin Y (photocatalyst) can effectively achieve the controllable polymerization of methyl methacrylate utilize CNCs as stabilizer. The polymerization in Pickering emulsion has relatively higher stability. The polymerizations of MMA showed typical "living"/controlled characteristics with controlled molecular weights (150,100 219,100 g/mol) and low Mw/Mn (1.10 1.25) CNCs can not only be recycled, but also can be applicable as one of the most robust "green" emulsifier for PET ATRP in Pickering emulsion.

title: Self healing nanocomposite hydrogels based on modified cellulose nanocrystals by surface initiated photoinduced electron transfer ATRP
abstract: Self healing hydrogels with excellent toughness and mechanical strength are particularly desirable for practical application. In this paper, green and environmentally friendly cellulose nanocrystals (CNCs) were successfully modified on the surface via metal free photoinduced electron transfer atom transfer radical polymerization (PET ATRP) Surface initiated PET ATRP was achieved by using 4 vinylpyridine (4VP) as functional monomer, 10 phenylphenothiazine (Ph PTZ) as photocatalyst and ultraviolet light (365 nm) as light source, respectively. The prepared P4VP CNCs hybrid materials (CNCs@P4VP) were used as green reinforcement to obtain self healing nanocomposite hydrogels by electrostatic interactions. As a result, the nanocomposite hydrogels displayed outstanding mechanical (6.6 MPa at a strain of 921.6% and self healing (85.9% after repairing 6 h) properties. This work provides a promising green method for designing novel self healing nanocomposite hydrogels with high strength.

title: Preparation of fluorescent cellulose nanocrystal polymer composites with thermo responsiveness through light induced ATRP
abstract: In recent years, cellulose nanocrystal (CNC) based materials have attracted great research attention for different applications owing to their unique properties and facile modification chemistry. In this work, CNC based thermo responsive fluorescent composites were successfully prepared via the metal free surface initiated atom transfer radical polymerization (ATRP) of NIPAAm and a Schiff base containing dye (HDPAP) Results demonstrated CNC poly (NIPAAm HDPAP) composites display sensitive temperature responsive coil to globule transition behavior at the temperature of lower critical solution temperature. The bright fluorescence offered by the Schiff base dye (HDPAP) was also confirmed by fluorescence spectra. Moreover, the preparation method of light meditated ATRP was proved to become the promising way in fabrication of multifunctional nanomaterials for its incomparable advantages, including low energy consumption, high efficiency, good monomer adaptation, free of transition metal ions.

title: Cellulose based phase change fibres for thermal energy storage and management applications
abstract: Phase change fibres (PCFs) with excellent thermal energy storage abilities and suitable tuneable temperature properties are of high interest for not only providing human comfort but also reducing energy waste. However, the complex fabrication process and the fragility and low durability of PCFs are issues that must be addressed to widen the scope of their application. Herein, a facile, environmentally friendly, and low cost strategy of photoinduced metal free surface initiated atom transfer radical polymerization (SI ATRP) was adopted to fabricate multifunctional cellulose based PCFs, which were composed of cellulosic fibres as supporting material s and poly (hexadecyl acrylate) (PA16) as phase change working substances. Through UV irradiation, PA16 was covalently grafted to the surface modified fibres and wrapped around them, which formed core shell like structures. The resulting PCFs exhibited high phase change enthalpies (73 J/g) excellent tensile strengths (10.5 MPa) and superhydrophobicity. Furthermore, the thermal management was investigated experimentally. The results demonstrated the outstanding thermal regulable properties. Thus, this work not only highlights the material design and preparation but also provides environmentally friendly and high performance PCFs with great potential application prospects for a variety of fields.

title: Riboflavin induced metal free ATRP of (meth)acrylates
abstract: Metal free ATRP approach was improved by eliminating undesirable organic photocatalyst from the reaction medium by an application of a fully biocompatible riboflavin (vitamin B2) based molecule playing two crucial roles in photoinduced polymerization as an ATRP initiator and photoinitiator simultaneously. The brominated ribitol tail constituted an ATRP initiator, while the unmodified isoalloxazine ring was excited to a highly reactive triplet excited state under blue light irradiation, and thus induced the photopolymerization of (meth)acrylates from the ribitol tail. The double initiation functionality of riboflavin provides brush like polymers with side chains composed of poly(ethylene glycol) methyl ether methacrylate (OEGMA500) with narrow molecular weight distribution (Mw/Mn 1.36) and preserved chain end functionality proved by successfully conducted chain extension experiment with the final product characterized by low dispersity (Mw/Mn 1.35) The riboflavin induced polymerization of OEGMA500 was temporally controlled by switching on off blue light irradiation without the loss of chain end functionality after restarting the synthesis, resulting in well defined polymer materials (Mw/Mn 1.37) The results indicate precisely established reversible redox cycle of the riboflavin photosensitizer during polymerization, providing equilibrium between the active and dormant species, and thus controlled polymer products. The double functional riboflavin molecule makes metal free ATRP approach an efficient and green chemistry solution for the preparation of functional polymer materials. The prepared riboflavin based brush like polymers were visualized by atomic force microscopy (AFM)

title: Synthesis of random copolymers of 4 vinylpyridinewith n octadecyl acrylate/n octadecyl methacrylateby metal free ATRP
abstract: Controlled radical polymerization (CRPs) has emerged as one of the most far reaching developments in polymer synthesis and has contributed fundamental techniques to prepare polymers with well defined structure and architecture [1, 2] Concerning CRP techniques, atom transfer radical polymerization (ATRP) is arguably the most utilized method as it is applicable to the polymer synthesis of a variety of monomers. One limitation of using ATRP is metal contamination of the products. Although metal loadings in a catalyst can be limited to parts per million (ppm) the residual metal in the products may cause difficulties in many sensitive applications such as biomaterials, microelectronics, etc  However, recently developed photocatalysts for ATRP have been introduced as a potential method to synthesise polymers with complete elimination of transition metal residue and thus be less affected by reaction media

title: Metal Free ATRP Catalyzed by Visible Light in Continuous Flow
abstract: ATRP of methyl methacrylate catalyzed by Eosin Y, an inexpensive and an environmental benign dye, was performed in a continuous flow reactor made of FEP tubing and irradiated by visible light green LEDs. The reaction under flow conditions was significantly more rapid and controlled compared to that in batch giving 90% of polymerization after only 3 h of irradiation. The formed polymers in flow have Mn measured by GPC and DOSY NMR in accordance with the theoretical values and show low dispersities (D 1.5) The livingness of the polymers has been confirmed by LED on and LED off experiments and by the synthesis of block copolymers. The protocol described herein serves as a "proof of concept" of using Eosin Y as a photocatalyst for controlled polymerization and of using 1D and 2D NMR for polymer characterization. The protocol could be replicated in the future for other reversible deactivation radical polymerizations.

title: Synthesis of Hyperbranched Polymers via Metal Free ATRP in Solution and Microemulsion