Photomediated atom transfer radical polymerization of MMA under long-wavelength light irradiation

In this study, a novel photocatalyst, pentarylenebis(dicarboximide) dye: (1,6,13,18-tetra(4-(2,3,3-trimethylbut-2-yl)phenoxy)-N,N’-(2,6-diisopropylphenyl)-pentarylene-3,4,15,16-tetracarboxidiimide) (TTPDPT), was first used in metal-free photoinduced atom transfer radical polymerization (ATRP) of methyl methacrylates (MMA). The initiator was methyl α-bromoisobutyrate (MBI) and the light source was mild near-infrared (NIR) light irradiation (λ_max?≈?870 nm). The TTPDPT-mediated ATRP relies on in situ photoreduction of a MBI through an electron transfer process to generate the desired alkyl radical, which could induce polymerization of the monomer. The photoinduced metal-free ATRP of MMA shows typical characteristics of controlled free radical polymerization, showing the linear evolution of number-average molecular weight (M_n,GPC) with monomer conversion, where polymers with predetermined degree of polymerization have well-controlled molecular weights and narrow molecular weight distribution (M_w/M_n). The photoinduced metal-free ATRP of MMA can be carried out with just ppm level of TTPDPT. The polymerization initiation and propagation can be operated by the aid of pulsed light sequences while NIR light source was used to promote carbon–carbon bond formation and to produce poly(methyl methacrylate) (PMMA) with M_w/M_n as low as 1.5. The synthesized PMMA was characterized by ¹H nuclear magnetic resonance (¹H NMR). The resultant PMMA contained a bromide end group that can be employed to reinitiate styrene polymerization to produce block copolymers through chain extension experiments.     

Ultralow ppm <Emphasis Type="Italic">se</Emphasis>ATRP synthesis of PEO-<Emphasis Type="Italic">b</Emphasis>-PBA copolymers

Poly(ethylene oxide)-block-poly(butyl acrylate) copolymers were prepared via simplified electrochemically mediated atom transfer radical polymerization (seATRP) utilizing only 1 ppm of Cu^II complex, which is the limit of a successful well-controlled polymerization. The presented seATRP system works under potentiostatic and galvanostatic conditions. The polymerization results showed similar molecular weight evolution while maintaining a narrow molecular weight distribution throughout the reactions. ¹H NMR results confirm chemical structure of synthesized diblock copolymers. This ultralow ppm technique is promising candidate for polymerization from nanoparticles, flat surfaces, proteins, and DNA.     

Photo-induced ATRP of MMA without ligands in ionic liquid

Fe-mediated photo-induced atom transfer radical polymerization (ATRP) of methyl methacrylate was studied with chlorophyll A as photoredox catalyst in the absence of ligands. This is the first report on photo-induced and FeBr₃-mediated ATRP. A low-cost and environmentally friendly ATRP is provided in this system. A good linear semi-logarithmic plot of polymerization kinetics is the first-order time conversion, and narrow molecular weight distributions explain the well-controlled behavior. The measured number average molecular weight, M _n,GPC (determined by gel permeation chromatography), is increased with monomer conversion, and it is in good agreement with the theoretical values (M _n,th). The effect of FeBr₃ is studied with respect to the polymerization. The values of the resultant PMMA increased with reduced FeBr₃ concentration. In this system, the effect of periodic light/off process has been investigated through chain growth instantly turned on and off in response to the visible light. The polymerization was controllable even though the concentration of Fe-based catalyst was dropped to 4 ppm. The chain-end group having a functionality in the synthesized poly(methyl methacrylate) was characterized by nuclear magnetic resonance spectrometry (¹H NMR). However, chain extension experiments show reserved chain-end functionality in the synthesized polymers and further confirm the “living” feature of the Fe-mediated photo-induced atom transfer radical polymerization.     

Polymerization of methyl methacrylate and acrylonitrile in the presence of copper BIAN complex

A novel type of copper-based regulating agents was first applied in radical polymerization of methyl methacrylate and acrylonitrile. It was shown that systems based on copper complex with redox-active bis(acetonaphthene) ligand (dpp-BIAN?CuCl)₂, carbon tetrachloride and different activating agents such as ascorbic acid or amines (tert-butylamine, diethylamine, triethylamine and pyridine) were capable to initiate polymerization of the above monomers in wide temperature range from 25 to 110 °C. The amine structure and basicity were found to make great impact on polymerization and molecular weight parameters of the obtained products. The systems developed are capable of conducting polymerization up to high monomer conversions in a wide temperature range leading to polymers with rather low molecular weight and moderate polydispersity. The most efficient system in terms of controlling the molecular weight characteristics of poly(methyl methacrylate) among others is the system based on (dpp-BIAN?CuCl)₂ and diethylamine, which makes it possible to obtain polymer with a polydispersity index of 1.36–1.60. In case of acrylonitrile polymerization, the highest polymer yield is achieved using a copper complex and triethylamine. The results of MALDI TOF mass spectroscopy measurements showed the presence of chlorine atoms at the chain ends of macromolecules. The formation of “living” chains during polymerization of methyl methacrylate was confirmed by the synthesis of block-copolymers with styrene.     

Development of nano-channel single crystals and verification of their structures by small angle X-ray scattering

Nano-channel single crystals were developed via consecutive growth of various polymer single-crystal channels comprising homo and block copolymers by self-seeding method. Poly(ethylene glycol)-b-polystyrene (PEG-b-PS) and poly(ethylene glycol)-b-poly(methyl methacrylate) (PEG-b-PMMA) block copolymers were synthesized by atom transfer radical polymerization. Self-seeding temperature, concentration, and crystallization time affected the width of the channels. This might provide a new way to investigate directional absorption, diffusion, and immobilization of biomacromolecules on the surface. The crystalline blocks of PEG-b-PS and PEG-b-PMMA diblock copolymers were similar, therefore, the continuity of channel-wire growth was guaranteed. Development of complete square channels next to the channels covered with high molecular weight brushes was infeasible. It was ascribed to a higher hindrance of primarily existing tethered chains on the single-crystal channel. Finally, the consecutive channel-wire single crystals were compared with single-step-grown pyramidal and conic structures. These multilayer crystals grew spirally and formed non-flat channels. The structure and morphology of different crystalline channels were detected by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). In this work, for the first time, the SAXS data of channel-wire single crystals were reported and they were compared by non-flat channel-like crystals. A profound investigation of PEG-b-PS, PEG-b-PMMA copolymers and PEG homopolymer channel-wire single crystals by SAXS and their comparison with AFM data was a novel work in the field of single-crystal engineering.     

A high molecular weight acrylonitrile copolymer prepared by mixed solvents polymerization: II. effect of DMSO/water ratios on polymerization and stabilization

A bifunctional comonomer β-methylhydrogen itaconate was synthesized to prepare high molecular weight poly [acrylonitrile-co-(β-methylhydrogen itaconate)] [P (AN-co-MHI)] by mixed solvents polymerization, which was used as carbon fiber precursor instead of acrylonitrile terpolymers. The effect of dimethyl sulfoxide (DMSO)/deionized water ratios on the polymerization, structure and stabilization of P (AN-co-MHI) was studied by elemental analysis, UV-Visible Spectroscopy, fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The highest viscosity-average molecular weight (76.72 × 10⁴ g/mol) of P(AN-co-MHI) was obtained in the mixed solvents of DMSO/deionized water = 10/90 (wt/wt) due to the zero chain transfer constant of deionized water for radical ~ ~ ~AN·, which is 10 times larger than that of P(AN-co-MHI) copolymers prepared in DMSO solution polymerization under the same conditions and is beneficial to improving the tensile strength of resulting carbon fiber. The composition of P(AN-co-MHI) was controlled by the ratio of DMSO/deionized water in the mixed solvents, it is attributed to the changes of AN/MHI ratio taking part in the polymerization reactions, which is caused by the different solubility of AN in the mixed solvents. From elemental analysis and FTIR studies, it can be found out that the content of MHI in P(AN-co-MHI) copolymer becomes larger with the increase of DMSO content in the mixed solvents. The FTIR, XRD and DSC results show that the stabilization of P(AN-co-MHI) copolymer was significantly improved by MHI compared with PAN homopolymer and poly (acrlonitrile-methyl acrylate-acrylic acid) terpolymer, such as larger extent of stabilization, lower initiation temperature and smaller E _a of cyclization, which is beneficial to preparing high performance carbon fiber.     

Aqueous radical polymerization of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylacrylamide redox-initiated by aerobically catalytic oxidation of water-soluble tertiary amines

Catalytic oxidation of water-soluble tertiary amines by complexes of Cu^II, Fe^III and Co^II was utilized to initiate radical polymerization of N,N-dimethylacrylamide (DMAAm) in aqueous solution at 70–80 °C. The oxidation of tertiary amines by Cu^II was studied by proton nuclear magnetic resonance spectroscopy and online ultraviolet–visible spectrophotometry. The polymerization kinetics was monitored by gas chromatography, and molecular weight of the PDMAAm was measured by gel-permeation chromatography coupled with multi-angle laser light scattering. Oxidation of tertiary amines occurs predominantly via formation of C_alpha·radicals to initiate polymerization of electron-deficient monomers and N-dealkylation, and redox equilibrium between Cu^I/L and Cu^II/L is established at a faster rate in aqueous media. Fe^III and Cu^II complexes are efficient catalysts as each catalyst molecule could generate above 10 propagating radicals in 5 h, while Co^II complex might involve in oxidation of tertiary amines in non-radical pathway, leading to a low catalytic efficiency. Water-soluble tertiary amines such as N,N-dialkylethanolamine (alkyl = methyl, ethyl etc.) are reducing agents of a higher activity in aqueous media than those primary or secondary analogues. Our strategy renders it possible to prepare polymer of alpha-amino functionality via one-pot process from commercially available commodity reagents under practical conditions with negligible catalyst residue.     

Well-defined dibenzocyclooctyne end functionalized polymers from atom transfer radical polymerization

The dibenzocyclooctyne end functionalized agent 1 was designed as atom transfer radical polymerization (ATRP) initiator. The ATRP was then explored on three types of monomers widely used in free radical polymerization: methyl methacrylate, styrene, and acrylates (n-butyl acrylate and tert-butyl acrylate). The living polymerization behaviors were obtained for the methyl methacrylate and styrene monomers. The SPAAC click reactivity of dibenzocyclooctyne end group were demonstrated by successfully reacting with azide functionalized small chemical agents and polymers. Various topological polymers such as block and brush polymers were produced from strain-promoted azide-alkyne cycloaddition reaction (SPAAC) using the resultant dibenzocyclooctyne end functionalized poly(methyl methacrylate)/polystyrene as building blocks. For the acrylates, however, the polymerization did not hold the living characteristics with the dibenzocyclooctyne end functionalized ATRP initiator 1.     

Synthesis of novel polymer brushes of poly(acrylonitrile-<Emphasis Type="Italic">g</Emphasis>-<Emphasis Type="Italic">N,N</Emphasis>ʹ-dimethylaminoethyl methacrylate) by nitrile modification

Functional polymer brushes of poly(acrylonitrile-g-N,N?-dimethylaminoethyl methacrylate) were efficiently synthesized by a novel approach of combining Cu(0)-mediated controlled/“living” radical polymerization and nitrile click chemistry. The poly(acrylonitrile-g-N,N?-dimethylaminoethyl methacrylate) as a promising material exhibited excellent hydrophile–lipohile balance in the process of self-assembly and could autonomously develop the orderly structure micelle in N,N?-dimethylformamide/water mixture solvent for the potential application of a new drug delivery carrier. In the process of self-assembly, polyacrylonitrile acted as a backbone of the functional polymer brushes due to its hydrophobic feature and poly(N,N?-dimethylaminoethyl methacrylate) as the branch of functional polymer brushes due to its hydrophilic characteristic, which both were prepared by Cu(0)-mediated controlled/“living” radical polymerization with ethyl-bromoisobutyrate as initiator. Poly(N,N?-dimethylaminoethyl methacrylate) containing azide end group was synthesized by substitution reaction of poly(N,N?-dimethylaminoethyl methacrylate) containing bromine end groups with sodium azide in N,N?-dimethylformamide. The click reaction between the nitrile of polyacrylonitrile and the azide group of poly(N,N?-dimethylaminoethyl methacrylate) was carried out under ammonium chloride as catalyst in N,N?-dimethylformamide. The polymer was further confirmed by GPC, FTIR, ¹H NMR and TGA. Meanwhile, the micelles with different morphologies were observed by TEM, and the particle diameter distribution of self-assembled micelle from the PAN-g-PDMAEMA brushes was determined by DLS.     

Catalytic Cu(II)–polymer complexes as recyclable catalysts for the synthesis of poly(2,6-dimethyl-1,4-phenylene oxide)s in water

Water-soluble polymers comprising itaconic amide acid with acrylic acid or acrylamide, which contain carboxylic acid and amide groups capable of coordinating to the copper catalyst, were synthesized by radical polymerization using an azobisisobutyronitrile initiator. These polymers were used as polymer ligands to prepare copper complexes, which were subsequently analyzed by UV–Vis spectroscopy. The complexes were then used as catalysts for the oxidative polymerization of 2,6-dimethylphenol (DMP) to synthesize poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) under oxygen and in the presence of a surfactant in alkaline water. The polymerization conditions were optimized by varying the amounts of polymer ligands and copper precursors, the concentrations of surfactant and hydrogen chloride, and the temperature, resulting in PPO with a maximum yield of 93%, a number-average molecular weight (M _n) of 3700, and a molecular weight distribution (M _w/M _n) of 2.12. This yield is higher than that previously achieved using arginine ligand in water (72%). Furthermore, the optimum conditions were applied in the copolymerization of DMP and 2-allyl-6-methylphenol to obtain a thermally crosslinkable copolymer in 95% yield (M _n = 3000, M _w/M _n = 2.5). In addition, the catalyst complex of the copper–polymer ligand was recovered and reused after the polymerization of DMP. The catalyst maintained its activity even after being recycled five times, without the addition of copper precursor or polymer ligand, thereby demonstrating an environmentally friendly process wherein environmental emissions and production costs can be substantially reduced.     

Effect of different structured POSS/GMA-containing copolymers on the morphology of porous coating by breath-figures method

Polyhedral oligomeric silsesquioxane (POSS) and glycidyl methacrylate (GMA) are used to synthesize linear L-(PGMA-b-MA-POSS), dicephalous D-(PGMA-b-MA-POSS)₂, and four-armed T-(PGMA-b-MA-POSS)₄ through atom transfer radical polymerization (ATRP). These different structured POSS/GMA-containing copolymers are applied to build the porous films through breath-figures (BF) method. L-(PGMA-b-MA-POSS) is easy to form the ordered porous BF film, and T-(PGMA-b-MA-POSS)₄ tends to form well-distributed BF film due to its high segment density which is beneficial to stabilize water drop. It is proven that solvent has a great effect on the morphologies of BF film. The perfect BF film is developed in the relatively wet atmosphere as 5–8 μm diameter of pores casted in THF and 2–4 μm diameter of pores casted in CH₂Cl₂ with regular morphology. The developed BF film has superior stability than the film developed in natural conditions due to the shorter stable balancing time. Therefore, it is believed that the obtained porous films show great potential in coating application.     

A new method in designing compatibility and adhesion of EVA/PMMA blend by using EVA-<Emphasis Type="Italic">g</Emphasis>-PMMA with controlled graft chain length

Atom transfer free radical polymerization (ATRP) was employed in a synthesis of graft polymer EVA-g-PMMA with controlled length of side PMMA chains. Three steps of synthesis: partial hydrolysis of EVA, esterification with chloroacetyl chloride and ATRP grafting were performed to produce EVAOH, macroinitiator EVACl and grafted polymers G8020 (EVA/PMMA?=?80/20 wt%) and G6040 (EVA/PMMA?=?60/40 wt%). FTIR, Raman and NMR spectroscopy were used in the determination of the chemical structure and modification of EVA. Transmitted light and dark field microscopy showed higher affinity for coil formation of EVA-g-PMMA with longer PMMA side chains, i.e. G6040 compatibilizer. Morphological, thermal and adhesive properties of optical fiber adhesives of graft polymers and polymer blends poly(ethylene-co-vinyl acetate)-blend-poly(methyl methacrylate) (EVA/PMMA) compatibilized with 1 wt% of EVA-g-PMMA, were studied. Image analysis of SEM micrographs showed effective compatibilization with short grafted chains (G8020) that was indicated by lower porosity characteristics. TG/DTG analysis enabled determination of degree of hydrolysis and amount of chloro-functionalized groups. DSC analysis showed higher thermal stability of G8020 polymer. Single lap joint of adhesives/optical fibers were subjected to adhesive testing and obtained results for maximal force applied and adhesive failure suggested the visible influence of the length of graft chains on adhesion.     

Modification of Silica Nanoparticles with Miktoarm Polymer Brushes via ATRP

Silica nanoparticles were successfully modified with miktoarm brushes via atom transfer radical polymerization (ATRP) using three different approaches. In the first approach: “graft onto and from”, a poly(tert-butyl acrylate) (PtBA) macroinitiator was grafted onto the surface of a monomer-modified silica nanoparticle. Then, polystyrene (PSt) brush was grafted from the surface-tethered reactive chain end. In the second approach: “two-step reverse ATRP”, the PtBA and poly(n-butyl acrylate) (PBA) brushes were consecutively grafted from initiator-modified silica particles via ATRP. The polymerization was initiated from the silica surface via a two-step controlled thermal decomposition of surface-tethered diazo initiator moieties. In the third method: “diblock first”, a diblock copolymer of poly(tert-butyl acrylate) and poly(glycidyl methacrylate) (PtBA-b-PGMA) was grafted onto amine-modified silica particles. The diblock copolymer was covalently attached to the silica surface via interaction between surface-tethered amine groups and the short reactive block containing glycidyl groups. Next, the polystyrene brushes were grafted from surface-tethered reactive chain end. The materials prepared by three different approaches were characterized using gel permeation chromatography (GPC) and thermogravimetric analysis (TGA). The PtBA brushes were hydrolyzed under acidic conditions to form poly(acrylic acid) (PAA) brushes. The resulting materials were imaged using atomic force microscopy (AFM) and transmission electron microscopy (TEM).     

Preparation of controlled molecular weight and narrow distribution HALS and its application

A polymerizable hindered amine light stabilizer (HALS) 1,2,2,6,6-pentamethyl-piperidin-4-yl acrylate (PMPA) was synthesized, and it was copolymerized with styrene to prepare poly(St-co-PMPA) by reversible addition fragmentation chain transfer (RAFT) polymerization. The reaction conditions, such as chain transfer agent (CTA)/initiator ratio, monomer/CTA ratio, and St/PMPA ratio, were found to affect the polymerization reaction. Poly(St-co-PMPA) with high molecular weight and narrow distribution could be obtained under suitable conditions. The molecular weight is about 3.0 × 10³ to 5.0 × 10³ and the molecular weight distribution is about 1.07 to 1.25. The result showed that PMPA was effectively added to the polymer chain and the polymerizations were found to proceed in controlled fashions under a lower conversion. Moreover, the tensile strength and notched impact strength of ABS/poly(St-co-PMPA) are significantly improved, respectively, after 800-h UV irradiation, which was both higher than that of pure ABS. The results showed that poly(St-co-PMPA) was an effective high molecular weight HALS.     

Synthesis and characterization of polyimides from 4,4′-(3-(<Emphasis Type="Italic">tert</Emphasis>-butyl)-4-aminophenoxy)diphenyl ether

A novel diamine 4,4′-(3-(tert-butyl)-4-aminophenoxy)diphenyl ether (4) was synthesized from 2-tert-butylaniline and 4,4′-oxydiphenol through iodination, acetyl protection, coupling reaction and deacetylation protection. Then some polyimides (PIs) were obtained by one-pot polycondensation of diamne 4 with several commercial aromatic dianhydrides respectively. They all exhibit enhanced solubility in organic solvents (such as NMP, DMF, THF and CHCl₃ etc.) at room temperature. Their number-average molecular weights are in the range of (2.1–3.7)?×?10⁴ g/mol with PDI from 2.25 to 2.74 by GPC. They can form transparent, tough and flexible films by solution-casting. The light transparency of them is higher than 90% in the visible light range from 400 nm to 760 nm and the cut-off wavelengths of UV–vis absorption are below 370 nm. They also display the outstanding thermal stability with the 5% weight loss temperature from 525 °C to 529 °C in nitrogen atmosphere. The glass transition temperatures (T _g s) are higher than 264 °C by DSC. XRD results demonstrate that these PIs are amorphous polymers with the lower water absorption (<0.66%). In summary, the incorporation of tert-butyl groups and multiple phenoxy units into the rigid PI backbones can endow them excellent solubility and transparency with relatively high T _g s.     

Novel amphiphilic temperature responsive graft copolymers PCL-<Emphasis Type="Italic">g</Emphasis>-P(MEO<Subscript>2</Subscript>MA-<Emphasis Type="Italic">co</Emphasis>-OEGMA) via a combination of ROP and ATRP: synthesis,characterization, and sol-gel transition

A series of well-defined novel amphiphilic temperature-responsive graft copolymers containing PCL analogues P(αClεCL-co-εCL) as the hydrophobic backbone, and the hydrophilic side-chain PEG analogues P(MEO₂MA-co-OEGMA), designated as P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) have been prepared via a combination of ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). The composition and structure of these copolymers were characterized by ¹H NMR and GPC analyses. The self-assembly behaviors of these amphiphilic graft copolymers were investigated by UV transmittance, a fluorescence probe method, dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results showed that the graft copolymers exhibited the good solubility in water, and was given the low critical temperature (LCST) at 35(±1) °C, which closed to human physiological temperature. The critical micelle concentrations (CMC) of P(αClεCL-co-εCL)-g-P(MEO₂MA-co-OEGMA) in aqueous solution were investigated to be 2.0 × 10^?3, 9.1 × 10^?4 and 1.5 × 10^?3 mg·mL^?1, respectively. The copolymer could self-assemble into sphere-like aggregates in aqueous solution with diverse sizes when changing the environmental temperature. The vial inversion test demonstrated that the graft copolymers could trigger the sol-gel transition which also depended on the temperature.     

Solvent optimization for efficient enzymatic monoacylglycerol production based on a glycerolysis reaction

This study was aimed at screening solvent systems of varying polarities to identify suitable solvents for efficient and practical enzymatic glycerolysis. Several pure solvents and solvent mixtures were screened in a batch reaction system consisting of glycerol, sunflower oil, and Novozym^® 435 lipase. Out of 13 solvents tested, tert-butanol and tert-pentanol were the only pure solvents suitable for a fast glycerolysis reaction with an acceptably high formation of MAG. In these systems, MAG contents of 68–82% were achieved within a few hours. Mixtures of tert-butanol/hexane, tert-pentanol/hexane, and tert-butanol/tert-pentanol in varying ratios also gave high MAG contents (58–78%). The tertiary alcohols tert-butanol and tert-pentanol, or mixtures of one of them with hexane, seemed to be the best choice among the solvents tested with respect to reaction efficiency, practical industrial applications, and steric hydroxyl group hindrance, which suppresses the ester formation with FA.     

Reinforcement effect of poly (methyl methacrylate)-<Emphasis Type="Italic">g</Emphasis>-cellulose nanofibers on LDPE/thermoplastic starch composites: preparation and characterization

The effect of cellulose nanofibers (CNFs) and poly [methyl methacrylate (MMA)]-grafted cellulose nanofibers (CNF-g-PMMA) on mechanical properties and degradability of a 75/25 low density polyethylene/thermoplastic starch (LDPE/TPS) blend was investigated. Graft copolymerization on CNFs was performed in an aqueous suspension by free radical polymerization using MMA as an acrylic monomer. In addition, a LDPE/TPS blend was reinforced by different amounts of CNFs (1–5 wt%) and CNF-g-PMMA (1–7 wt%) using a twin-screw extruder. A 61% grafting of PMMA on the surface of CNFs was demonstrated by gravimetric analysis. Moreover, after modification the X-ray photoelectron spectroscopy analysis showed a 20% increase of carbon atoms on the surface of CNFs and a 22.6% decrease in the oxygen content of its surface. The mechanical properties of the CNFs-modified composites were significantly improved compared to the unmodified nanocomposites. The highest tensile strength and Young’s modulus were obtained for the composites reinforced by 3 and 7 wt% CNF-g-PMMA, respectively. The degradability of cellulose nanocomposites was studied by water absorption and soil burial tests. Surface modification of CNFs lowered water absorption, and soil burial test of the LDPE/TPS blend showed improvement in biodegradability by addition of CNF-g-PMMA.     

Synthesis of all-acrylic graft copolymers by grafting-through strategy in emulsion

In this paper, PnBA-g-PMMA brush-like and centipede multigraft copolymers were synthesized via DPE seeded emulsion polymerization and miniemulsion polymerization. PMMA macromonomers with single tail and double tails were prepared by DPE-technique in emulsion and Steglich esterification. Then PnBA-g-PMMA multigraft copolymers were obtained by miniemulsion copolymerization. The molecular weight and polydispersity indices of PMMA macromonomers and graft copolymers were characterized by GPC. The structural characteristics, weight content of PMMA and the number of grafting sites in brush-like and centipede multigraft copolymers were determined by ¹H NMR. The thermal performance of graft copolymers were analyzed by DSC and TGA. AFM confirmed microphase separation between PnBA block and PMMA block.