Monomer Feed Ratio Research Articles

Controlled Radical Polymerization of Acrylates and Isocyanides Installs Degradable Functionality into Novel Copolymers.

Installing ketones into a polymer backbone is a known method for introducing photodegradability into polymers; however, most current methods are limited to ethylene-carbon monoxide copolymerization. Here we use isocyanides in place of carbon monoxide in a copolymerization strategy to access degradable nonalternating poly(ketones) that either maintain or enhance the thermal properties. A cobalt-mediated radical polymerization of acrylates and isocyanides synthesizes nonalternating poly(acrylate-co-isocyanide) copolymers with tunable incorporation using monomer feed ratios. The kinetic product of the polymerization is a dynamic β-imine ester that tautomerizes to the β-enamine ester. Hydrolysis of this copolymer affords a third copolymer microstructure─the elusive nonalternating poly(ketone)─from a single copolymerization strategy. Analysis of the copolymer properties demonstrates tunable thermal properties with the degree of incorporation. Finally, we show that poly(acrylate-co-isocyanide) and poly(acrylate-co-ketone) are photodegradable with 390 nm light, enabling chain cleavage.

4D printing of biodegradable elastomers with tailorable thermal response at physiological temperature

4D printing has a great potential for the manufacturing of soft robotics and medical devices. The alliance of digital light processing (DLP) 3D printing and novel shape-memory photopolymers allows for the fabrication of smart 4D-printed medical devices in high resolution and with tailorable functionalities. However, most of the reported 4D-printed materials are nondegradable, which limits their clinical applications. On the other hand, 4D printing of biodegradable shape-memory elastomers is highly challenging, especially when transition points close to physiological temperature and shape fixation under ambient conditions are required. Here, we report the 4D printing of biodegradable shape-memory elastomers with tailorable transition points covering physiological temperature, by using poly(D,L-lactide-co-trimethylene carbonate) methacrylates at various monomer feed ratios. After the programming step, the high-resolution DLP printed stents preserved their folded shape at room temperature, and showed efficient shape recovery at 37 °C. The materials were cytocompatible and readily degradable under physiological conditions. Furthermore, drug-loaded devices with tuneable release kinetics were realized by DLP-printing with resins containing polymers and levofloxacin or nintedanib. This study offers a new perspective for the development of next-generation 4D-printed medical devices.

Tailoring the properties in conjugated copolymer P(EDOS-co-EDOT): Electrochemical polymerization and role of heteroatom

Considering the significant work on copolymerization, very little is known about the copolymerization of two heteroaromatic rings to generate new properties. In this work, we report a series of conducting copolymers [poly(3,4-ethylenedioxyselenophene)-co-poly(3,4-ethylenedioxythiophene)] [denoted as P(EDOS-co-EDOT)] synthesized via anodic polymerization using different feed ratios of two engaged monomers. Three feed ratios of monomers 3,4-ethylenedioxyselenophene (EDOS) and 3,4-ethylenedioxythiophene (EDOT) were used as 5:1, 1:1, and 1:5 for electrochemical copolymerization in acetonitrile containing 0.1 M tetrabutylammonium perchlorate as a supporting electrolyte. Corresponding homopolymers PEDOS and PEDOT were also prepared from monomers EDOS and EDOT, respectively, by electrochemical polymerization to sight the analogy and differences in the properties of obtained copolymers with respect to individual homopolymers. Copolymers were structurally characterized via Raman spectroscopy and X-ray fluorescence. The redox traits, optoelectronic properties and surface morphology of as-prepared polymer films were characterized using cyclic voltammetry, spectroelectrochemistry and field emission scanning electron microscope, respectively. Electrochemical stability of the copolymers was examined by repeating redox cycles. Density functional theory calculations were carried out to get an understanding of the trends in energy levels, and comparisons were made with the experimental results. Copolymer films exhibited deep blue color in the neutral state while transmissive gray in oxidized state. Electrochromic properties of the copolymers were carried out, and found highest optical contrast ratio to be 36.86% and coloration efficiency of 62.89 cm2 C − 1 for 1:5 ratio. It was found that all the copolymers have different highest occupied molecular orbital (HOMO) levels resulting from their distinct redox behavior and band gap values lie within the range of homopolymers. Thus, copolymerization is an effective route for the synthesis of polymer to tune the properties for electronic applications.

Preparation and Characterization of fluorinated copolymer emulsion for concrete protection

Emulsifier-free copolymerizations of 2,2,2-trifluoroethyl 2-methylpropanoate (TFMPA) and methyl acrylate in the presence of surface-active commoner, undecylenic acid (UA), were carried out using potassium persulfate (KPS) as initiator. The prepared copolymer emulsions were characterized and analyzed by FT-IR, 1H and 19F NMR spectra, TEM, dynamic light scattering (DLS), and contact angle testing. The results showed that the average particle size of copolymer latex particles was 200-300 nm with a relatively uniform particle size distribution. The glass transition temperature was controlled with the monomer feed ratios. After copolymer emulsions coating on the concrete surface, the contact angle was significantly increased, and the water absorption of the concrete was significantly reduced.

Synthesis and Evaluation of Alginate-Based Nanogels as Sustained Drug Carriers for Caffeine.

The objective of this study is to design a polymeric network of nanogels for sustained release of caffeine. Therefore, alginate-based nanogels were fabricated by a free-radical polymerization technique for the sustained delivery of caffeine. Polymer alginate was crosslinked with monomer 2-acrylamido-2-methylpropanesulfonic acid by crosslinker N',N'-methylene bisacrylamide. The prepared nanogels were subjected to sol-gel fraction, polymer volume fraction, swelling, drug loading, and drug release studies. A high gel fraction was seen with the increasing feed ratio of polymer, monomer, and crosslinker. Greater swelling and drug release were observed at pH 4.6 and 7.4 as compared to pH 1.2 due to the deprotonation and protonation of functional groups of alginate and 2-acrylamido-2-methylpropanesulfonic acid. An increase was observed in swelling, loading, and release of the drug with the incorporation of a high feed ratio of polymer and monomer, while a reduction was seen with the increase in crosslinker feed ratio. Similarly, an HET-CAM test was used to evaluate the safety of the prepared nanogels, which showed that the prepared nanogels have no toxic effect on the chorioallantoic membrane of fertilized chicken eggs. Similarly, different characterizations techniques such as FTIR, DSC, SEM, and particle size analysis were carried out to determine the development, thermal stability, surface morphology, and particle size of the synthesized nanogels, respectively. Thus, we can conclude that the prepared nanogels can be used as a suitable agent for the sustained release of caffeine.

Nonstoichiometric Migita-Kosugi-Stille Coupling Polycondensation based on Intramolecular Catalyst Transfer System

In this paper, a nonstoichiometric Migita-Kosugi-Stille coupling polycondensation based on intramolecular catalyst transfer systems has been reviewed. The achievement of those systems is significant from the viewpoints of (1) acquisition of new knowledge in the synthesis of semiconducting polymer materials, (2) unnecessary strict control in monomer feed ratios generally required for a single-phased solution polycondensation, (3) possible improvement of the monomer reactivity by varying feed ratios, and (4) possibility of controlled chain end groups and extension to the synthesis of all-conjugated block copolymers. In practice, naphthalene-diimide-, phthalimide-, and terephthalate-based π-conjugated polymers have been synthesized under imbalanced stoichiometric conditions, possessing much higher molecular weights than those based on Carothers/Flory’s theory. The results of various model reactions and DFT calculations have revealed that the origin of the intramolecular catalyst transfer phenomenon is related to the existence of carbonyl groups introduced at the ortho-position of dibromo aryl monomers used in excess as well as types of palladium catalysts/precatalysts. In the near future, the proposed nonstoichiometric Migita-Kosugi-Stille coupling polycondensation will be established by extending the adaptable monomers and further optimizing catalysts/precatalysts.

Facile preparation of isocyanate-functionalized poly(styrene-co-maleimide-co-maleic anhydride) particle and its application as a versatile support for nano-sized TiO2 photocatalyst

Polymer-supported catalysts have attracted intensive research attentions due to easy handling, facile separation and outstanding recycling performance. Herein, a simple, efficient and universal strategy was developed to fabricate isocyanate-functionalized polymer microspheres bearing highly reactive surface isocyanate groups, which could serve as a versatile support for the immobilization of photocatalyst. Firstly, self-stabilized precipitation polymerization of maleimide, maleic anhydride and styrene was performed in the presence of divinyl benzene (crosslinker) to prepare imide-functionalized poly(styrene-co-maleimide-co-maleic anhydride) (PSMM) microspheres. By simply adjusting the solvent composition and monomer feed ratio, monodisperse PSMM particles with diameter in the range of 0.52–1.01 μm were successfully obtained, which were further modified with hexamethylene diisocyanate (HDI). As a proof-of-concept, TiO2 nanoparticles were readily and covalently bound to the surface of HDI-functionalized PSMM (PSMM-HDI) particles through reaction with isocyanate groups, leading to the formation of PSMM-HDI supported TiO2 (PSMM-HDI@TiO2). Furthermore, anhydride groups on the surface of PSMM was hydrolyzed to endow PSMM-HDI@TiO2 with better dispersibility and adsorption performance. The degradation of methylene blue under UV-light was performed to evaluate the photocatalytic performance of the resultant PSMM-HDI@TiO2. Compared with pristine TiO2, the PSMM-HDI@TiO2 exhibited not only higher degradation efficiency, but also facile separation and better reusability.

Copolymerization of 4‐vinylsulfonyl aniline with acrylamide and its application as macromolecular dye backbone

AbstractA kind of copolymer, poly(4‐vinylsulfonylaniline‐co‐acrylamide) (P(VSA‐co‐AM)), was synthesized by the copolymerization of 4‐vinylsulfonyl aniline (VSA) and acrylamide (AM) using tetrahydrofuran (THF) as the solvent and 2,2′‐azobis(2‐methylpropionitrile) (AIBN) as the initiator in the presence of a total monomer mass concentration of 15%, and a polymerization duration of 10 h. The effect of the monomer feed ratio on the copolymerization is investigated, and the results reveal that increasing the content of VSA in the monomer feed ratio increases the proportion of VSA in the copolymer. A feed ratio of 5:5 is selected for the copolymerization of VSA and AM, and a copolymer with 28% VSA is obtained. After diazotization, P(VSA‐co‐AM) with a molecular weight of 4.45 × 103 and a VSA ratio of 28% is coupled with the coupling component containing more chloro‐s‐triazine reactive groups, thus resulting in macromolecular reactive dyes. The fixation of the obtained macromolecular reactive dyes A, B, and C on cotton fabric is over 93% and have good light, rubbing, and washing fastnesses, thus indicating their potential application in the dyeing of cotton fabric.

Mass spectrometry insight into the electro-copolymerization mechanism of aniline with o-phenylenediamine

It has been a challenge to accurately characterize the chain growth mechanism during copolymerization. Herein, an electrochemistry-microtube-mass spectrometry (EC-mTube-MS) was developed for on-line monitoring of aniline (ANI) electro-copolymerized with o-phenylenediamine (oPD). Short-lived intermediates and co-oligomers belonging to polyANI-oPD were structural identified with tandem MS method for the first time. The free binding between ANI and oPD monomers determined the presence of more species for a given co-n-mer. Chain growth was found to compete with 2H+, 2e− intramolecular oxidation of co-oligomers, resulting in the units with quinone or phenazine structures. MS signals for polyANI and polyoPD were observed as well, indicating that the homopolymerization occurred simultaneously with the copolymerization, which may affect the formation efficiency even performance of the final copolymer. Investigations on the monomer feed ratio and solution pH provided data support for improving the copolymerization efficiency, and the recommended parameters are cANI: coPD ≥ 10:1 and pH = 7.

Synthesis and Characterization of Copolymers from Diallyldimethylammonium Hexafluorophosphate and Methyl Methacrylate

This work presents the radical copolymerization of diallyldimethylammonium hexafluorophosphate (DADMA(PF6)) and methyl methacrylate (MMA) with minimal added solvent. The ion exchange of DADMAC from chloride to hexafluorophosphate yielded a water-insoluble form of the ammonium monomer that is soluble in MMA. Copolymerizations were successfully carried out over a wide range of monomer feed ratios, which correlated strongly to the composition of the final copolymer and made it possible to incorporate large percentages of either monomer. Studies of copolymer composition at a range of reaction times indicated that the incorporation of MMA was slightly favored over that of DADMA(PF6). While all copolymers formed water-insoluble stand-alone films, qualitative examination of the films demonstrated that those with high incorporations of MMA had greater flexibility and optical clarity. A facile, reproducible polymerization method developed herein produced copolymers containing diallyldimethylammonium moieties that can be processed into water-insoluble polymer films for potential membrane applications.

PREPARATION AND PROPERTIES OF CHLORINATED POLYISOBUTYLENE ELASTOMER BY ONE-STEP POLYMERIZATION

ABSTRACT Cationic copolymerization of isobutylene and chlorostyrene was investigated using the Lewis acid initiator system. Titanium (IV) chloride (TiCl4) and ethylaluminum sesquichloride (AlEt1.5Cl1.5) were used as the co-initiators, and 2-chloro-2,4,4-trimethylpentane (TMPCl) and H2O were used as the main initiators. The influences of monomer feeding ratio and reaction time were studied. The reaction mechanism was proposed by studying the reaction kinetics. It was found that when p-chloromethylstyrene (p-ClMSt) was used, benzyl chloride was easily involved in the initiation reaction stage, leading to the formation of branched polymer. When p-chlorostyrene (p-ClSt) was used as a co-monomer, living copolymerization was achieved and no branching structure formed. Isobutylene, isoprene, and p-ClSt were synthesized with the AlEt1.5Cl1.5 initiator system. The high-molecular-weight halogenated ternary copolymer was successfully prepared by one-step polymerization. Vulcanization and mechanical property studies were also performed.

Fully tuneable ethylene-propylene elastomers using a supported permethylindenyl-phenoxy (PHENI*) catalyst.

Using a highly active supported permethylindenyl-phenoxy (PHENI*) titanium catalyst, high molecular weight ethylene-propylene (EPM) and ethylene-propylene-diene (EPDM) elastomers are prepared using slurry-phase catalysis. Final copolymer composition was found to reflect the monomer feed ratio in a linear fashion, to access a continuum of material properties with a single catalyst. Post-polymerisation crosslinking of EPDM was also demonstrated in a model sulfur vulcanisation system.

Copolymers of 4-Trimethylsilyl Diphenyl Acetylene and 1-Trimethylsilyl-1-Propyne: Polymer Synthesis and Luminescent Property Adjustment

Poly(4-trimethylsilyl diphenyl acetylene) (PTMSDPA) has strong fluorescence emission, but its application is limited by the effect of aggregation-caused quenching (ACQ). Copolymerization is a commonly used method to adjust the properties of polymers. Through the copolymerization of 4-trimethylsilyl diphenyl acetylene and 1-trimethylsilyl-1-propyne (TMSP), we successfully realized the conversion of PTMSDPA from ACQ to aggregation-induced emission (AIE) and aggregation-induced emission enhancement (AEE). By controlling the monomer feeding ratio and with the increase of the content of TMSDPA inserted into the copolymer, the emission peak was red-shifted, and a series of copolymers of poly(TMSDPA-co-TMSP) that emit blue-purple to orange-red light was obtained, and the feasibility of the application in explosive detection was verified. With picric acid (PA) as a model explosive, a super-quenching process has been observed, and the quenching constant (KSV) calculated from the Stern-Volmer equation is 24,000 M-1, which means that the polymer is potentially used for explosive detection.

Development and Optimization of Tamarind Gum-β-Cyclodextrin-g-Poly(Methacrylate) pH-Responsive Hydrogels for Sustained Delivery of Acyclovir.

Acyclovir has a short half-life and offers poor bioavailability. Its daily dose is 200 mg five times a day. A tamarind gum and β-cyclodextrin-based pH-responsive hydrogel network for sustained delivery of acyclovir was developed using the free-radical polymerization technique. Developed networks were characterized by FTIR, DSC, TGA, PXRD, EDX, and SEM. The effect of varying feed ratios of polymers, monomers, and crosslinker on the gel fraction, swelling, and release was also investigated. FTIR findings confirmed the compatibility of the ingredients in a new complex polymer. The thermal stability of acyclovir was increased within the newly synthesized polymer. SEM photomicrographs confirmed the porous texture of hydrogels. The gel fraction was improved (from 90.12% to 98.12%) with increased reactant concentrations. The pH of the dissolution medium and the reactant contents affected swelling dynamics and acyclovir release from the developed carrier system. Based on the R2 value, the best-fit model was zero-order kinetics with non-Fickian diffusion as a release mechanism. The biocompatibility of the developed network was confirmed through hematology, LFT, RFT, lipid profile, and histopathological examinations. No sign of pathology, necrosis, or abrasion was observed. Thus, a pH-responsive and biocompatible polymeric system was developed for sustained delivery of acyclovir to reduce the dosing frequency and improve patient compliance.

Hunting black color via absorption engineering: EDOT and thiophene-benzothiadiazole based black-to-transmissive copolymer and its electrochromic device application

Neutral state black electrochromics are prominent materials for smart applications such as displays, car rear views, e-papers etc. This work has aimed to obtain a neutral state black electrochromic polymer, by tuning the optical absorbance to whole visible region. Two monomers, 4,7-bis(5-(thiophen-2-yl)thiophen-2-yl)benzo[c] [1,2,5]thiadiazole (TTBTT) and 3,4-ethylenedioxythiophene (EDOT), were selected according to their complementary absorbance behaviors, and they were combined in the same polymer backbone via electrochemical copolymerization technique. Copolymerization was performed using three different monomer feed ratios (2:1, 1:1 and 1:2 (EDOT: TTBTT)). Even though all the copolymers exhibited dark to transmissive colors from neutral to oxidized states, changing the monomer feed resulted in different optical contrast, switching response and color hues for each copolymer. The higher optical contrast (from 17% to 27%) and faster switching response (from 3.6 s to 1.8 s) were recorded as EDOT unit increase in the copolymer chain. A dual type electrochromic device was also constructed using the copolymer and the resulting device was successfully changed its color from black to transmissive.

Effect of monomer composition on thermal, mechanical, and self-healing properties of thermosets containing Diels-Alder adduct moieties and disulfide bonds

The Diels-Alder (DA) and thiol-maleimide reactions of difurfuryl disulfide (DFDS), 1,4-bismaleimidodiphenylmethane (BMI), pentaerythritol tetrakis(3-mercaptopropionate) (PETMP), and thiol-terminated disulfide-containing polyether (LP) at various feed monomer ratios produced polymer networks containing both DA adduct moieties and disulfide bonds. Fourier transform infrared spectral analysis revealed that the DA and thiol-maleimide reactions occurred for all the cured products. A differential thermal analysis revealed that all the cured products exhibited an endothermal peak due to the retro-DA reaction at 115–124 °C. The tensile moduli and strengths of the cured products increased with increasing DFDS (or DA) and PETMP fractions. The elongations at break increased with increasing LP (or disulfide) fraction. Most of the cured products exhibited self-healing ability by annealing at 60 °C for 24 h, and/or at 120 °C for 1 h followed by additional annealing at 60 °C for 24 h. The cured product with a higher LP (or disulfide) fraction exhibited a better healing ability at 60 °C for 24 h by the disulfide metathesis. Also, the cured product with a higher DFDS fraction exhibited a better healing ability at 120 °C for 1 h and 60 °C for 24 h by the DA/retro-DA reaction.

Controlling shape morphing and cell release in engineered living materials

Engineered living materials (ELMs) derive functionality from both a polymer matrix and the behavior of living cells within the material. The long-term goal of this work is to enable a system of ELM-based medical devices with both mechanical and bioactive functionality. Here, we fabricate multifunctional, stimuli-responsive ELMs comprised of acrylic hydrogel matrix and Escherichia coli. These ELMs undergo controlled changes in form and have a controlled release of bacteria from the composite. We hypothesize that the mechanical forces associated with cell proliferation within a covalently-crosslinked, non-degradable hydrogel are responsible for both phenomena. At constant cell loading, increased hydrogel elastic modulus significantly reduces both cell delivery and volume change associated with cell proliferation. ELMs that change volume over 100 % also result in ~106 colony forming units/mL in the growth medium over 2 h after 1 day of growth. At constant monomer feed ratios, increased cell loading leads to significantly increased cell delivery. Finally, these prokaryotic ELMs were investigated for their potential to deliver a probiotic that can reduce the proliferation of a uropathogen in vitro. Controlling the long-term delivery of bacteria could potentially be used in biomedical applications to modulate microbial communities within the human body.

Novel polyaniline/8-hydroxyquinoline composite electrode materials for simultaneous electrochemical removal of heavy metal ions from water resources

Herein, polyaniline/8-hydroxyquinoline (PAn-HQ) composites with various monomer feed ratios were developed as novel and efficient electrode materials to remove heavy metal ions including Hg(II), Cd(II), Pb(II), Cu(II), Ni(II), and Zn(II) from water resources. Besides detailed structural, morphological, and thermal stability studies, electrochemical properties of fabricated composites were investigated. Compare with PAn with increasing HQ concentration in the initial feed ratio, more resistant, compact, and sticky structures were observed, as well as excellent mechanical and thermal stability of the composites. Due to significant features of the prepared composites, the considerable removal capacity of heavy metal ions has been achieved through electrodeposition technique. Optimum experimental conditions such as HQ concentration, electrodeposition time, ionic strength, pH, and metal ion concentration were considered. Based on our findings, using 0.06 M HQ concentration, remarkable heavy metal ion removal occurs in an aqueous solution with adjusted pH including 1.0 M KNO3 and 50 mg L−1 initial concentration of metal ion during 24 min electrodeposition. The desorption study by the eluting adsorbent in deionized water at time intervals and adjusted acidic pH values revealed that the initial removal capability of the PAn-HQ composites preserves even after 10 cycles of electrodeposition/desorption. Finally, as-prepared PAn-HQ composites were employed to remove heavy metal ions from a collected real sample from Caspian Sea. The modified PAn-HQ electrodes fabricated via a facile and manageable electrochemical procedure are believed to offer significant adsorption capacity in environmental remediation to remove heavy metal ions.

Versatile Copolymer for Stretchable and Self-healable Liquid-free Ionic Conductive Elastomers.

To facilitate the practical use of ionic conductive materials for flexible electronics, the issues existing in hydrogels and ionogels, such as low thermostability and possible solvent leakage, need to be resolved but are inevitable. Liquid-free ionic elastomers (ICEs) as an alternative option are free of such concerns but have been facing the drawbacks of low conductivity and less satisfying mechanical properties. Here, a versatile copolymer with π-π stacking and cation-π interactions for high-performance ICE is proposed. The ICEs presented tunable mechanical and electrical properties by varying the feed ratio of the ternary monomers. The optimized ICE possessed high stretchability and strength, fast shape-recovery, self-healing, decent conductivity, and desirable stability against heat and under ambient conditions. The use of virgin and self-healed ICEs as the conductors for dielectric elastomer actuators (DEA) is demonstrated and exhibits comparable actuating performance to the reported DEA employing organogels and ionogels. The work provides a facile approach for fabricating ICEs with versatile properties that can be used for flexible electronics.

ICAR ATRP-induced surface self-assembly in the fabrication of the surface nanostructures

Polymerization induced surface self-assembly (PISSA) technology is a state-of-the-art method in the fabrication of the hierarchical surface nanostructures. Previously, we demonstrated that reversible addition−fragmentation chain transfer (RAFT) polymerization-based PISSA could be used to construct hierarchical surface nanostructures on the silica particles. Atom transfer radical polymerization (ATRP) has many advantages, especially in the synthesis of the macroinitiator. In this research initiators for continuous activator regeneration (ICAR) ATRP-induced PISSA approach is used to fabricate surface nanostructures. Poly(ethylene glycol) (PEG) macroinitiator and poly(oligo(ethylene glycol) monomethyl ether methacrylate-co-2-(2-bromoisobutyrnyloxy) ethyl methacrylate) (P(OEGMA-co-BIEM)) polymer brush macroinitiator on silica particles are used to initiate ATRP of styrene in methanol/water mixture. With the chain extensions, POEGMA-g-PS graft copolymer brushes and “free” PEG-b-PS block copolymer chains make surface coassembly into surface nanostructures. With an increase in monomer feeding ratio, the surface morphology gradually changes from small-sized spherical surface micelles (s-micelles), to big-sized s-micelles, and to asymmetric layered structures. Kinetics studies indicate that with an increase in monomer conversion there is a transition from homogeneous to heterogeneous polymerization.