Preparation Of Copolymers Research Articles

Preparation of Supramolecular Miktoarm Star Copolymers with a Zinc Phthalocyanine Core through ATRP and RAFT Polymerization.

Topological polymers have attracted considerable attention owing to their unique chemical and physical properties. This study demonstrates the formation of novel supramolecular miktoarm star copolymers with a zinc phthalocyanine (ZnPc) core using metal-ligand coordination interactions. Various linear polymers with pyridyl end groups, poly(methyl methacrylate), poly(vinyl acetate) and poly(N-vinyl carbazole), are prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. This facilitates coordination to the ZnPc core of 4-armed star-shaped polystyrene prepared via atom-transfer radical polymerization (ATRP). Furthermore, the formation of a 1:1 complex of a ZnPc molecule and pyridyl group of the chain-transfer agent for RAFT is confirmed by absorption spectral studies and 1 H NMR spectroscopic analyses. The concept of supramolecular complexation can be extended to the preparation of AB4 -type supramolecular miktoarm star-shaped copolymers with functional cores.

Copolymers Derived from Two Active Esters: Synthesis, Characterization, Thermal Properties, and Reactivity in Post-Modification.

Copolymers with two distinguished reactive repeating units are of great interest, as such copolymers might open the possibility of obtaining selective and/or consequent copolymers with different chemical structures and properties. In the present work, copolymers based on two active esters (pentafluorophenyl methacrylate and p-nitrophenyl methacrylate) with varied compositions were synthesized by Cu(0)-mediated reversible deactivation radical polymerization. This polymerization technique allows the preparation of copolymers with high to quantitative conversion of both comonomers, with moderate control over dispersity (Đ = 1.3–1.7). Additionally, by in-depth study on the composition of each copolymer by various techniques including elemental analysis, NMR, FT-IR, and XPS, it was possible to confirm the coherence between expected and obtained composition. Thermal analyses by DSC and TGA were implemented to investigate the relation between copolymers’ composition and their thermal properties. Finally, an evaluation of the difference in reactivity of the two monomer moieties was confirmed by post-modification of copolymers with a primary amine and a primary alcohol as the model.

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Construction of a Stimuli-Responsive DNAzyme-Braked DNA Nanomachine for the Amplified Imaging of miRNAs in Living Cells and Mice

Preparation of chitosan-graft N-hydroxyethyl acrylamide copolymers as an in vitro-engineered skin

Amino-polysaccharides derivatives such as grafted chitosan (CS) have attracted increasing interest in biotechnology. The work aims to assess the novel CS-g-PHEAA as a model for in vitro-engineered skin. Gamma radiation-induced copolymerization has achieved N-hydroxyethyl acrylamide (HEAA) grafting onto CS. The functionalization of CS by the amino group has been confirmed through solid-state carbon-13 nuclear magnetic resonance. As evidenced by cell metabolic activity, viability, and proliferation results of human dermal fibroblast (HDF) co-cultivated with the biomaterials, the biological assays are independent of the choice of solvent. Also, the grafting degree, the HDF growth, and monolayer migration favored using CS-g-PHEAA prepared in bulk. Hence, it has potential as a future bioengineered skin substitute material.

Preparation of Copolymer of Allyl Ester of Salicylic Acid with Styrene and Study of Its Antifungal Properties

Preparation of Copolymer of Allyl Ester of Salicylic Acid with Styrene and Study of Its Antifungal Properties

Preparation A Cross-Linked Copolymer By Using Unsaturated Poly(2-Butene Maleate) Polyester and Methyl Methacrylate

In this study, synthesis of unsaturated Poly(2-Butene Maleate) polyester by condensation polymerization and preparation of cross-linked graft copolymer with methyl methacrylate are presented. For this purpose, unsaturated polyesters were synthesized in four different time periods (12h, 24h, 36h, 48h) in the presence of hydroquinone using 1,4-Butanediol-2-ene and maleic anhydride. Then, the obtained unsaturated polyester was purified on the alumina column and used to obtain cross-linked copolymer with methyl methacrylate. Here in, methyl methacrylate acts as both co-monomer and cross-linking agent.
 In the preparation of Poly(2-Butene Maleate), the optimization study of the molecular weight and yield ratios with the time parameter was carried out. In the results obtained, it was observed that the maximum molecular weight was reached after almost 36 hours (Mn=3400). It was observed that time did not have much effect on the yield. Structural characterizations of the obtained products were supported by FT-IR and NMR analyzes. In thermal analysis, it was observed that the thermal stability of Cross-linked graft copolymer is higher than unsaturated polyester but lower than pure Poly(methyl methacrylate).

Preparation of starch-acrylic acid-carboxymethyl cellulose copolymer and its flocculation performance towards methylene blue

Flocculants synthesized from biopolymers show the virtues of low cost, excellent efficiency and environmental friendliness. In this study, starch-acrylic acid-carboxymethyl cellulose (SAC) tertiary anionic copolymers were prepared by graft copolymerization. The optimal synthesis process was determined as raw material ratio of 1:3:1, acrylic acid neutralization degree of 70%, initiator dosage of 1.0 wt%, reaction temperature of 75 °C and reaction time of 5 h according to the flocculation performance towards methylene blue simulated waste water. Results demonstrated that the decolorization ratio of methylene blue (100 mg/L) could be up to 81.3% at the SAC dosage of 350 mg/L. The SAC achieved rapid flocculation kinetics and excellent color removal over a broad range of pH, ambient temperature and ionic strength. Furthermore, the operation cost of SAC is only one-fourth of industrial anionic polyacrylamide. The prepared SAC flocculant is promising for industrial dye wastewater treatment owing to its green raw materials, high efficiency and low operation cost.

Controlled alcoholysis of PET to obtain oligomers for the preparation of PET-PLA copolymer

Controlled degradation of macromolecules or natural macromolecules is important for their subsequent utilization. Normally, it is easier to degrade them to monomers than to oligomers in designated molecular weight range, the controlled degradation is much difficult to achieve and has been challenge for the utilization of macromolecules. Here, we proposed a strategy for simultaneous degradation of the inner and outer layers of PET, which avoid the degradation of polymers from the outside to the inside and achieved the controlled degradation. Under high temperature and micro-pressure conditions, PET is transformed from dense to flocculent structure by the swelling effect, which satisfies the need for simultaneous degradation of the inner and outer layers. In addition, a stable “Dawson” type Polyoxometalates (POMs) α2-K8P2W17O61X(H2O)‧16H2O (X = Zn, Mn, Co, Ni, Cu) with limited number of catalytic activity center was synthesized and applied to PET alcoholysis to obtain oligomer with given molecular weight range. Under the optimal conditions, PET: EG: POM catalyst = 1.0: 4.0: 0.02 (wt%), 240 °C, 10 min, PET was completely degraded and obtained the oligomer products (Mn < 2000 g/mol) with 72.1 % yield. By investigating the mechanism of the controlled alcoholysis, the formation of flocculent PET was be the key factor in achieving controlled degradation; hydrogen bonding and coordination of POMs are the key interactions to achieve rapid alcoholysis. Finally, oligomers were applied in the preparation of PET-PLA copolymers to follow sustainable route. The incorporation of bio-based polymers demonstrates better inclusiveness to the environment and contributes to harmonious development.

One-Pot Reactive Melt Recycling of PLA Post-Consumer Waste for the Production of Block Copolymer Nanocomposites of High Strength and Ductility.

Post-consumer waste recycling is a crucial issue for building a sustainable society. However, mechanical recycling of poly(lactic acid) (PLA) often reduces the performance of the recycled material because PLA has a strong tendency to degrade during reprocessing. Therefore, it is of great interest to develop an effective recycling method to improve the mechanical performance of this material. This paper presents a one-pot melt process for turning PLA waste into a biodegradable block copolymer and its high strength and ductility composite. The process was conducted in a melt-mixer through a transesterification of PLA with poly(ethylene glycol) (PEG) or poly(propylene glycol) (PPG) as a soft component and clay as reinforcement. Effects of soft component content and sequence of clay addition on the mechanical performance of the prepared materials were focused. The results showed the successful preparation of PLA-based multiblock copolymers of high molecular weights (~100 kDa). Both virgin PLA and recycled source could serve as the starting material. PEG was more efficient than PPG in providing an intense improvement of PLA ductility. The nanocomposite of intercalated structure yielded nearly 100 times higher elongation at break (Eb = 506%) than the starting PLA (Eb = 5.6%) with high strength of 39.5 MPa and modulus of 1.4 GPa, considering the advantages of clay addition. Furthermore, the products with a broadened range of properties can be designed based on the ratio of PLA and soft component, as well as the organization and spatial distribution of clay in the copolymer matrices.

Synthesis and Characterization of Ibuprofen Delivery System Based on β-cyclodextrin/Itaconic Acid Copolymer

This study aims at preparation and characterization of drug delivery system based on grafted beta-cyclodextrin (β-CD) with itaconic acid (IA) using free-radical copolymerization technique, in the presence of N, N'-methylene bisacrylamide (BIS) and ammonium persulphate (APS) as a crosslinker and an initiator, respectively. The obtained copolymer (CD-PIA) was characterized using Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction patterns (XRD), transmission and scanning electron microscopes (TEM and SEM). Ibuprofen (IBU), as an anti-inflammatory drug model, was loaded during the preparation. The kinetic of the copolymerization was investigated in terms of grafting yield (GY %), grafting efficiency (GE %) and monomer conversion (%). Moreover, in vitro IBU release and kinetic of released using the different mathematical models (0-order, first-order and Higushi) were carried out in simulated gastric and intestinal fluids (SGF and SIF at pH 1.2 and 7.4, respectively) at 37 °. The results proved the successful preparation of the target copolymer with irregular spherical-like shape and particle size around 14 - 27.7 nm. After IBU loading, the copolymer exhibited thermal stability with crystalline nature. Also, the study showed that the synthesized copolymer, especially which high IA content is controlled the release of IBU after 4 h. Besides, it could be used as a potential IBU delivery system with sustained-release followed the first-order kinetic over 24 h.&#x0D; HIGHLIGHTS&#x0D; &#x0D; The nanogels drug carriers used for nonsteroidal anti-inflammatory drugs to overcome the unfavorable release in the stomach due to unforeseen pH alterations&#x0D; The polymeric grafted β-CD derivatives using IA represent a unique class of the host materials with tunable inclusion properties and high affinity for Ibuprofen release&#x0D; In vitro kinetic of IBU released showed the best fit with first-order model&#x0D; &#x0D; GRAPHICAL ABSTRACT

Polypyrrole–polyaniline-water hyacinth leaf protein concentrate composite for the removal of Cr(VI) from aqueous solution: kinetics, isotherm and thermodynamic studies

ABSTRACT. This work focused on the extraction of “water hyacinth leaf protein concentrate” (WHLPC) and preparation of polypyrrole (PPy), polyaniline (PANI) and polypyrrole-polyaniline copolymer (PPy/PANI) coated WHLPC by in situ polymerization and investigate their application for the removal of Cr(VI) from aqueous solution. After optimizing the experimental conditions like pH, adsorbent dosage, contact time and initial concentration it was found that the kinetics and isotherm data were well fitted to the pseudo-second-order and Langmuir models, respectively. PPy/PANI/WHLPC was found to be an efficient material compared to the other polymer-coated adsorbents with maximum adsorption capacity of 230 mg/g. The presence of counter ions ((NO3-, Cl-, HPO42-, SO42+ and HCO3- ions) slightly decreases the Cr(VI) removal efficiency PPy/PANI/WHLPC. The thermodynamic study reveals that the adsorption of Cr(VI) onto PPY/PANI/WHLPC is endothermic, thermodynamically feasible, and spontaneous. In addition, reusability of the material indicated high removal efficiency for two adsorption cycles.&#x0D; &#x0D; KEY WORDS: Polypyrrole, Polyaniline, Protein concentrate, Water hyacinth, Chromium&#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(3), 571-584. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i3.7

Synthesis and Characterization of Copolymers and Nanocomposites from Limonene, Styrene and Organomodified-Clay Using Ultrasonic Assisted Method.

In the present work, we report a simple synthesis method for preparation of copolymers and nanocomposites from limonene and styrene using clay as a catalyst. The copolymerization reaction is carried out by using a proton exchanged clay as a catalyst called Mag-H+. The effect of temperature, reaction time and amount of catalyst were studied, and the obtained copolymer structure (lim-co-sty) is characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (1H-NMR) and differential scanning calorimetry (DSC). The molecular weight of the obtained copolymer is determined by gel permeation chromatography (GPC) and is about 4500 g·mol−1. The (lim-co-sty/Mag 1%, 3%, 7% and 10% by weight of clay) nanocomposites were prepared through polymer/clay mixture in solution method using ultrasonic irradiation, in the presence of Mag-CTA+ as green nano-reinforcing filler. The Mag-CTA+ is organophilic silicate clay prepared through a direct exchange process, using cetyltrimethylammonuim bromide (CTAB). The prepared lim-co-sty/Mag nanocomposites have been extensively characterized by FT-IR spectroscopy, X-ray diffraction (XRD), scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). TEM analysis confirms the results obtained by XRD and clearly show that the obtained nanocomposites are partially exfoliated for the lower amount of clay (1% and 3% wt) and intercalated for higher amounts of clay (7% and 10% wt). Moreover, thermogravimetric analysis (TGA) indicated an enhancement of thermal stability of nanocomposites compared with the pure copolymer.

Subcritical Water as a Pre-Treatment of Mixed Microbial Biomass for the Extraction of Polyhydroxyalkanoates.

Polyhydroxyalkanoate (PHA) recovery from microbial cells relies on either solvent extraction (usually using halogenated solvents) and/or digestion of the non-PHA cell mass (NPCM) by the action of chemicals (e.g., hypochlorite) that raise environmental and health hazards. A greener alternative for PHA recovery, subcritical water (SBW), was evaluated as a method for the dissolution of the NPCM of a mixed microbial culture (MMC) biomass. A temperature of 150 °C was found as a compromise to reach NPCM solubilization while mostly preventing the degradation of the biopolymer during the procedure. Such conditions yielded a polymer with a purity of 77%. PHA purity was further improved by combining the SBW treatment with hypochlorite digestion, in which a significantly lower hypochlorite concentration (0.1%, v/v) was sufficient to achieve an overall polymer purity of 80%. During the procedure, the biopolymer suffered some depolymerization, as evidenced by the lower molecular weight (Mw) and higher polydispersity of the extracted samples. Although such changes in the biopolymer’s molecular mass distribution impact its mechanical properties, impairing its utilization in most conventional plastic uses, the obtained PHA can find use in several applications, for example as additives or for the preparation of graft or block co-polymers, in which low-Mw oligomers are sought.

Synthesis and characterization of star-shaped block copolymers composed of poly(3-hydroxy octanoate) and styrene via RAFT polymerization

This study investigated a macro reversible addition fraction chain transfer (RAFT) agent based on three-arm hydroxylated star-shaped poly(3-hydroxy octanoate). The utilization of this star-shaped poly(3-hydroxy octanoate) macro-RAFT agent in the RAFT process resulted in efficient control in the preparation of star-shaped block styrene copolymers. Poly(3-hydroxy octanoate) (PHO) was reacted with diethanol amine (DEA) in order to obtain three-arm hydroxylated poly(3-hydroxy octanoate) (PHO-DEA). A carboxylic acid-functionalized RAFT agent (2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid) was reacted with the PHO-DEA in order to obtain a star-shaped PHO macro-RAFT agent (PHO-R2). A series of AB3 type PHO-polystyrene (PHO-PS) star-shaped block copolymers were obtained via the polymerization of styrene (S) using the PHO-R2 in toluene at 80 °C. The RAFT polymerization was seen to obey the polymerization kinetics of controlled free radical polymerization. The plasticizing effect of the PHO soft segments was influenced by the glass transition temperature (Tg) of polystyrene. This was clearly observed in the block copolymers. Moreover, it was clear that this plasticizing effect disappeared in the block copolymers as a result of the increase in polymerization time. The molar masses of the obtained copolymers increased in parallel with increases in the polymerization time. Structural, physiochemical, and thermal characterization of the obtained products was carried out using size-exclusion chromatography (SEC), proton nuclear magnetic resonance (1H NMR), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA) techniques. The polymerization kinetics of the star-shaped block copolymers were also investigated in detail.

Preparation and characterization of novel functional tri-block copolymer for constructing temperature/redox dual-stimuli responsive micelles

Herein, we reported a novel tri-block copolymer synthesized by segmented ring-opening polymerization of temperature-sensitive 5-(pyrrolidine-1-carbonyl) oxepan-2-one monomer (VPyCL) and redox-sensitive macrocyclic disulfide-substituted carbonate monomer (MSS). The structure of the copolymers was confirmed by GPC, 1H NMR and 13C NMR. The obtained tri-block copolymers could self-assemble in aqueous solution to form well-structured micelles, with the mPEG-b-PVPyCL block acting as the hydrophilic coronal and the PSS block acting as the hydrophobic core. Dynamic light scattering (DLS) studies confirmed that micelles formed by these tri-block copolymers with different block ratios could respond to different temperature ranges during the heating/cooling process and respond to reducing agent glutathione (GSH). In addition, transmission electron microscopy (TEM) results further confirmed the polymeric micelles’ dual-stimuli responsiveness. The potential application of this type of dual-stimuli responsive micelles in drug delivery systems was evaluated using doxorubicin (DOX) as the model molecule. The stimulus-dependent responsive behaviors of obtained micelles can be applied to the construction of smart materials capable of performing multiple functions under the appropriate conditions.

Preparation of cross-linking PVA copolymer modified by DAAM/ADH and application in paper surface sizing

Preparation of cross-linking PVA copolymer modified by DAAM/ADH and application in paper surface sizing

Preparation of Well-Controlled Isotactic Polypropylene-Based Block Copolymers with Superior Physical Performance via Efficient Coordinative Chain Transfer Polymerization

Preparation of Well-Controlled Isotactic Polypropylene-Based Block Copolymers with Superior Physical Performance via Efficient Coordinative Chain Transfer Polymerization

One‐For‐All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT

AbstractThis work develops the Polyolefin Active‐Ester Exchange (PACE) process to afford well‐defined polyolefin–polyvinyl block copolymers. α‐Diimine PdII‐catalyzed olefin polymerizations were investigated through in‐depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro‐mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and photoiniferter reversible addition–fragmentation chain transfer (PI‐RAFT). The significant difference in the properties of polyolefin–polyacrylamide block copolymers was harnessed to carry out polymerization‐induced self‐assembly (PISA) and study the nanostructure behaviors.

One-For-All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT.

This work develops the Polyolefin Active-Ester Exchange (PACE) process to afford well-defined polyolefin-polyvinyl block copolymers. α-Diimine PdII -catalyzed olefin polymerizations were investigated through in-depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro-mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring-opening polymerization (ROP), nitroxide-mediated polymerization (NMP), and photoiniferter reversible addition-fragmentation chain transfer (PI-RAFT). The significant difference in the properties of polyolefin-polyacrylamide block copolymers was harnessed to carry out polymerization-induced self-assembly (PISA) and study the nanostructure behaviors.

Hydrophobic core-hydrophilic shell graft block copolymers for unimolecular observation by AFM

Graft block copolymers for unimolecular observation by AFM are designed considering polymer morphology and affinity to substrate. For the observation on hydrophilic mica substrate, graft block copolymers with hydrophobic polystyrene (PS) core-hydrophilic poly(2-vinylpyridine) (P2VP) shell are successfully synthesized via anionic grafting polymerization from lithiated poly(p-methylstyrene) (PpMS). Preparation of the graft block copolymers are achieved by adding 2VP monomer to the chain end active PpMS-g-PS. As a confirmation of synthesis, AFM measurement clearly shows the molecules having a worm like structure lying on mica. According to cross-sectional analysis, the AFM image would be explained by aggregated PS core and extended P2VP shell. This reveals that controlling morphology of graft block copolymers on the substrate is achieved by designing side chains using segment affinities to the substrate.