Monomer Sequence Distribution Research Articles

Fine-Tuning Gradient Copolymers with Diverse and Controlled Microstructure and Mechanical Properties via Monomer Sequence Distribution: An In Silico Study

Fine-Tuning Gradient Copolymers with Diverse and Controlled Microstructure and Mechanical Properties via Monomer Sequence Distribution: An In Silico Study

Synthesis, kinetic study and characterization of C5‐dienes/styrene copolymers via living anionic polymerization in cyclopentyl methyl ether solvent

Abstract1,3‐Dienes/styrene sequence‐controlled copolymers are widely used as thermoplastic elastomers, transparent impact resin and synthetic rubber and other materials. In this work, the binary anionic copolymerization of styrene (S) and C5‐dienes including 1,3‐pentadiene (P, E/Z = 65/35) and isoprene (I) were studied in cyclopentyl methyl ether (CPME) ‘green’ solvent using n‐BuLi as initiator, and the effects of copolymerization monomer ratio and polar additive (PA) on the copolymerization kinetics and monomer sequence distributions were investigated. The kinetic analysis results showed that all copolymerization systems were the first‐order reaction and the C5‐dienes/S could be quantitatively consumed. The addition of S or I was conducive to the efficient conversion of P. Although the addition of PAs had little effect on the polymerization rate, it had a great influence on the microstructure and sequence distribution of the copolymer. 1H NMR tracking analysis showed that, for S/P copolymerization with different feeding ratios 1/3 < fP < 2/3, the instant composition FP in the copolymer remained relatively constant at 15% < FP < 35% when the monomer conversion rate was below 60%, and thus the inevitable formation of P microblocks in subsequent polymerization sequences was observed. Additionally, similar sequence distributions were obtained in the case of I/P copolymerization systems. By contrast, S/I copolymerization conformed to the typical random copolymerization pattern, and the copolymerization activity of S was slightly higher than that of the I in CPME. The use of strong PAs such as 2,2‐di(2‐tetrahydrofuran)propane directly resulted in a change of monomer sequence from a random pattern to a gradual block pattern. Moreover, the 3,4‐isoprene branch units were much more sensitive to solvent and PA than 1,2‐pentadiene units for C5‐dienes; also Fourier transform infrared and DSC analysis verified the microstructure and sequence analysis results mentioned above. In addition, the results of gel permeation chromatography showed that the copolymerization process in CPME had excellent controllable characteristics. © 2023 Society of Industrial Chemistry.

Influence of Monomer Sequence on the Cyclization Behavior of Poly(acrylonitrile-co-acrylamide)

In this research, we have developed the approach to controlled synthesis of acrylonitrile-acrylamide copolymers with narrow molecular weight distribution and various monomer sequence distributions. By using dibenzyl trithiocarbonate and batch/semibatch polymerization, we have first synthesized random, gradient, and block-gradient copolymers containing 3.4–10.2 mol. % of acrylamide and revealed the influence of the monomer sequence on the cyclization behavior of poly(acrylonitrile-co-acrylamide) by combination of differential scanning calorimetry and Fourier transform infrared spectroscopy. This allowed us to find differences in cyclization behavior of the copolymers in argon and air atmosphere. Intramolecular cyclization was the main process proceeding in argon atmosphere. The radical mechanism of cyclization was suppressed already at the molar part of acrylamide units in copolymer exceeding ~3 mol. % for random copolymer and ~6 mol. % for block-gradient copolymer. The activation energy of ionic cyclization was equal to 89 ± 3 kJ·mol−1 and was not influenced by both copolymer composition and chain microstructure in contrast to the rate of cyclization. The latter was increased with the rise of acrylamide content, the content of hetero-triads and in the range block-gradient < gradient < random structure. In air atmosphere, the oxidation reactions dominated over cyclization. The oxidation reactions were found to be less sensitive to copolymer composition and chain microstructure.

Synthesis of Random, Gradient, and Block-like Terpolycarbonates via One-Pot Terpolymerization of Epoxide, CO2, and Six-Membered Cyclic Carbonates

Multi-polymerization is regarded as a valuable strategy to tailor material performances by incorporating well-chosen monomers and tuning monomer sequence distributions in the polymer backbones. Despite that considerable advances have been made in the past decades, the modification of CO2-based polycarbonate materials is still in its infancy. In this contribution, a series of polycarbonate terpolymers with diverse chain structures were fabricated through a dissymmetric Cr complex-catalyzed one-pot terpolymerization of cyclohexene oxide (CHO), CO2 with six-membered cyclic carbonates (6CCs). The reaction conditions (temperature, feeding ratio, and CO2 pressure) as well as the 6CC substituents played a critical role in tailoring the sequence distributions of CHO/CO2/6CC terpolymers from random to gradient or block-like sequences. It was noteworthy that the average lengths of both sequences could be modulated by adjusting the feeding monomer ratios or reaction temperature, as detected by quantitative 13C NMR spectroscopy of purified terpolymers. Besides, DSC revealed that the glass-transition temperature of the obtained terpolymers had a wide range of 69.5–115.5 °C based on the polymer architecture.

Microstructural Analysis of Poly(ethylene-co-propylene-co-1-butene) terpolymers by Multidimensional NMR Spectroscopy

Physical, rheological and optical properties of polymer depend on its molecular microstructure. Specifically, the monomer content and sequence distribution of polymer significantly affect the mechanical performance of the final product. To this base, Nuclear Magnetic Resonance Spectroscopy (NMR) has been introduced as a very powerful technique to study the microstructure of polymer. The purpose of this study was to develop a methodology to investigate the microstructure of poly(ethylene-co-propylene-co-butene) terpolymer by using multidimensional NMR spectroscopy, including pulsed-field-gradient (PFG) 1H-13C heteronuclear single quantum coherence (GHSQC), heteronuclear multiple bond coherence (gHMBC), and heteronuclear single quantum coherence-total correlation spectroscopy (GHSQC-TOCSY). The combination of 1D and 2D NMR experiments, permit the characterization of the complex structure of poly(ethylene-co-propylene-co-butene) terpolymer. The completed 13C NMR assignments provided in this work allow more accurate quantitative determination of the microstructure in these polymers.

Determination of Chemical Composition and Monomer Sequence Distributions of Methacrylate Copolymers by Multivariate Analysis of NMR Spectra

Determination of Chemical Composition and Monomer Sequence Distributions of Methacrylate Copolymers by Multivariate Analysis of NMR Spectra

Machine learning strategies for the structure-property relationship of copolymers

SummaryEstablishing the structure-property relationship is extremely valuable for the molecular design of copolymers. However, machine learning (ML) models can incorporate both chemical composition and sequence distribution of monomers, and have the generalization ability to process various copolymer types (e.g., alternating, random, block, and gradient copolymers) with a unified approach are missing. To address this challenge, we formulate four different ML models for investigation, including a feedforward neural network (FFNN) model, a convolutional neural network (CNN) model, a recurrent neural network (RNN) model, and a combined FFNN/RNN (Fusion) model. We use various copolymer types to systematically validate the performance and generalizability of different models. We find that the RNN architecture that processes the monomer sequence information both forward and backward is a more suitable ML model for copolymers with better generalizability. As a supplement to polymer informatics, our proposed approach provides an efficient way for the evaluation of copolymers.

Controlling monomer sequence distribution in RAFT polymerization of styrene and acrylic acid

Continuous and semicontinuous RAFT copolymerization was first applied to synthesize well-defined copolymers of styrene and acrylic acid. The obtained copolymers have a different monomer sequence distribution due to different ways of adding acrylic acid to the reaction medium.

Strategy for Synthesis of Statistically Sequence-Controlled Uniform PLGA and Effects of Sequence Distribution on Interaction and Drug Release Properties.

Extensive studies have been conducted to elucidate the effects of such parameters as molecular weight, polydispersity, and composition on the controlled release properties of poly(d,l-lactic-co-glycolic acid) (PLGA). However, studies dealing with the effect of monomer sequence distribution have been sparse mainly because of the difficulty of precisely controlling the monomer sequence in PLGA. Herein, we present a semibatch copolymerization strategy that enables the production of statistically sequence-controlled "uniform PLGA" polymers through control of the rate of comonomer addition. Using this method, a series of PEG-PLGA samples having a comparable molecular weight and composition but different sequence distributions (uniform vs gradient) were prepared. The properties of these materials (PEG crystallization/melting, hygroscopicity, aqueous sol-gel transition, drug release kinetics) were found to significantly vary, demonstrating that sequence control only at the statistical level still significantly influences the properties of PLGA. Most notably, uniform PLGA exhibited the more sustained drug release behavior compared to gradient PLGA.

Mathematical Modeling of Free Radical Solution Terpolymerization Reactions in a Batch and Continuous Flow Stirred Tank Reactors

AbstractA mathematical model that describes a free radical solution terpolymerization is applied to styrene (St), methyl methacrylate (MMA), and maleic anhydride (MAh) polymerization system. This terpolymerization model allows for the use of either monofunctional or bifunctional peroxide initiators, and it is applied to batch and continuous reactions. The key model outputs are global monomer conversion, terpolymer composition, terpolymer average molecular weights, and terpolymer monomer sequence distributions. A few kinetic parameters are estimated such that global conversion is properly predicted by the model including initiator efficiency and two termination rate constants. Molecular weights are shown to be dominated by chain transfer reactions. Experimental trends of conversion, terpolymer molar masses (molecular weights), and composition are reasonably well predicted by the model.

Sequence-regulated vinyl polymers via iterative atom transfer radical additions and acyclic diene metathesis polymerization

Iterative ATRAs and ADMET polymerization enabled the synthesis of sequence-regulated vinyl polymers without statistical distribution of monomer compositions and sequences.

Synthesis, Characterization and Reactivity Ratios of Poly Phenyl Acrylamide-Co-Methyl Methacrylate

The monomer phenyl acrylamide was synthesized by reacting acrylamide with chloro benzene in the presence of pyridine. Copolymer of phenyl acrylamide (PAM) with methyl methacrylate (MMA) was synthesized by free radical technique using dimethylsulfoxide (DMSO) as solvent and benzoyl peroxide (BPO) as initiator. The overall conversion was kept low (≤ 15% wt/wt) for all studies copolymers samples. The synthesized copolymers were characterized using fourier transform infrared spectroscopy (FT-IR), and their thermal properties were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The copolymers compositions were determined by elemental analysis. The monomer reactivity ratios have been calculated by linearization methods proposed by Kelen-Tudos and Fineman-Ross. The derived reactivity ratios (r1, r2) for (PAM-co-MMA) are: (0.03, 0.593). The microstructure of copolymers and sequence distribution of monomers in the copolymers were calculated by statistical method based on the average reactivity ratios and found that these values are in agreement with the derived reactivity ratios. Copolymers of PAM with MMA formed alternating copolymers.

Characterization of Comb Shaped MAA‐co‐PEGMA Copolymers Synthesized by Free‐Radical Polymerization

AbstractMethacrylic acid‐co‐polyethylene glycol methacrylate (MAA‐co‐PEGMA) copolymers (also known as MPEG‐type polycarboxylate ether (PCE) superplasticizers) present comb‐shaped microstructure and they are generally used as dispersants of inorganic particles in cementitious formulations. Application properties of the PCEs strongly depend on the molecular structure and therefore accurate characterization of the microstructure is necessary to fully understand the structure–property relationship. In this work, MAA‐co‐PEGMA copolymers with various lateral size chain lengths and homogeneous copolymer compositions are synthesized by starved‐feed semibatch copolymerization. Molar mass and radius of gyration distributions and monomer sequence distribution are measured using size exclusion chromatography coupled with multi angle light scattering (SEC/MALS/refractive index, RI) and 1H and 13C NMR, respectively. Furthermore, it is proved that the experimental radius of gyration compares well with the prediction of a theoretical model for the radius of gyration that uses characteristic parameters of the microstructure of the PCEs (e.g., average molar masses). This confirms the accuracy of the measurements of the absolute molar masses for the MPEG‐type PCEs synthesized by free‐radical (co)polymerization.

Study of Copolymerization Acrylamide with Methyl Methacrylate

Copolymer of acrylamide (AM) with methyl methacrylate (MMA) was synthesized by free radical technique using dimethylsulfoxide (DMSO) as solvent and benzoyl peroxide (BPO) as initiator. The overall conversion was kept low (≤ 15% wt/wt) for all studies copolymer’s samples. The synthesized copolymers were characterized using fourier transform infrared spectroscopy (FT-IR), and their thermal properties were studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The copolymers compositions were determined by elemental analysis. The monomer reactivity ratios have been calculated by linearization methods proposed by Kelen-Tudos and Fineman-Ross. The derived reactivity ratios (r1, r2) for (AM-co-MMA) are: (0.03, 0.593). The microstructure of copolymers and sequence distribution of monomers in the copolymers were calculated by statistical method based on the average reactivity ratios and found that these values are in agreement with the derived reactivity ratios. Copolymers of AM with MMA formed alternating copolymers. Keywords: Acrylamide; Methyl methacrylate; Reactivity ratios; Sequence distribution

Studying Reactivity Relationships of Copolymers N-naphthylacrylamide with (Acrylicacid and Methylacrylate)

The organation ⁄monomer N-naphthylacrylamide (NAA) was prepared; subsequently the synthesized monomer was successfully copolymerized with acrylicacid (AA) and methylacrylate (MA) by free radical technique using dry benzene as solvent and benzoyl peroxide (BPO) as initiator. The overall conversion was kept low (≤ 10% wt/wt) for all studies copolymers samples. The synthesized monomer and copolymers were characterized using Fourier transform infrared spectroscopy (FT-IR), and their thermal properties were studied by DSC and TGA. The copolymers compositions were determined by elemental analysis. Kelen-Tudes and Finmman-Ross graphical procedures were employed to determine the monomers reactivity ratios. The derived reactivity ratios (r1, r2) are: (0.048, 0.687) for (NAA-co-AA) and (0.066, 0.346) for (NAA-co-MA). Based on the average reactivity ratios, sequence distribution of monomers in the copolymers and the microstructure of copolymers were calculated by statistical method and found that these values are in agreement with the derived reactivity ratios.

Studying Reactivity Relationships of Copolymers N-naphthylacrylamide with (Acrylicacid and Methylacrylate)

The organation ⁄monomer N-naphthylacrylamide (NAA) was prepared; subsequently the synthesized monomer was successfully copolymerized with acrylicacid (AA) and methylacrylate (MA) by free radical technique using dry benzene as solvent and benzoyl peroxide (BPO) as initiator. The overall conversion was kept low (≤ 10% wt/wt) for all studies copolymers samples. The synthesized monomer and copolymers were characterized using Fourier transform infrared spectroscopy (FT-IR), and their thermal properties were studied by DSC and TGA. The copolymers compositions were determined by elemental analysis. Kelen-Tudes and Finmman-Ross graphical procedures were employed to determine the monomers reactivity ratios. The derived reactivity ratios (r1, r2) are: (0.048, 0.687) for (NAA-co-AA) and (0.066, 0.346) for (NAA-co-MA). Based on the average reactivity ratios, sequence distribution of monomers in the copolymers and the microstructure of copolymers were calculated by statistical method and found that these values are in agreement with the derived reactivity ratios.

Propagation-Inspired Initiation of an Aliphatic Sodium Amidate for the Living Anionic Homo- and Copolymerization of Isocyanates: Access to the Multiblocky Sequence Distribution of Binary Comonomers

We report the propagation-inspired initiation of sodium N-phenethyl-3-phenylpropanamide (NaPEPPA), an aliphatic sodium amidate, for the living anionic homo- and copolymerization of isocyanates. This initiator was compared with sodium benzanilide (NaBA), an aromatic sodium amidate, in the living anionic homopolymerization of n-hexyl isocyanate (HIC). Only NaPEPPA attained the initiation efficiencies close to unity at the early stage of propagation. The homopolymerization with [HIC]0/[NaPEPPA]0 = 38.9/85.1/203 led to poly(n-hexyl isocyanate)s (PHICs) with predictable MWs and low dispersities (Mn,theo = 5.12/10.7/24.7 kDa; Mn = 5.22/11.1/27.4 kDa; Đ = 1.11/1.10/1.06). NaPEPPA was also used to initiate the living anionic copolymerization of HIC and furfuryl isocyanate (FIC). As a result, poly(furfuryl isocyanate-block-n-hexyl isocyanate) (P(FIC-b-HIC)) was afforded by the blocky monomer sequence distribution. Based on the copolymerization kinetics, a series of polyisocyanate-based multiblock copolymers, P(FIC...

Alternating Placement of d‐ and l‐Alanine Moieties in the Polymer Side‐Chains

AbstractSynthesis of a sequence‐controlled polymer via reversible addition‐fragmentation chain transfer polymerization is reported herein, using an N‐substituted maleimide monomer bearing tert‐butyl carbamate (Boc)‐protected l‐alanine (M1) and Boc‐d‐alanine appended styrenic monomer (M2). The monomer sequence distribution along the polymer chain is thoroughly studied by 1H and 13C NMR spectroscopy and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, confirming the alternating placement of l‐alanine and d‐alanine throughout the polymer chain. Copolymers display fluorescence properties in various organic solvents. After the deprotection of Boc‐groups, the copolymers show fluorescence activity in water (and also in several organic solvents), and pH‐responsiveness in aqueous medium due to the protonation/deprotonation of the side‐chain ‐NH2 groups at varying aqueous solution pH. In addition, the presence of different enantiomeric structures of alanine in the side‐chain enables us to investigate the chiroptical properties of the polymers.

Synthesis, chain structures and phase morphologies of trans-1,4-poly(butadiene-co-isoprene) copolymers

High trans-1,4-poly(butadiene-co-isoprene) (TBIR) copolymers from the stereo-selective and chemo-selective copolymerization of butadiene (Bd) and isoprene (Ip) are reported with MgCl2 supported Ziegler-Natta catalyst (TiCl4/MgCl2Al(i-Bu)3). Three major components in the copolymers, separated by stepwise isothermal crystallization fractionation, consist of crystalline trans-1,4-polyisoprene (TPI) blocks and trans-1,4-polybutadiene (TPB) blocks but in varied sequence length. Unique phase morphologies with different crystalline lamellar structures are observed in these TBIR copolymers for the first time. The phase morphologies of TBIR reflecting as the discrete lamellar stacks of TPB blocks and dendrimer-shaped lamellae of TPI blocks become diverse in different components with the varied statistical monomer and comonomer unit sequence distribution. The copolymers with TPB blocks are produced in the initial polymerization stage from the active species with relatively low stereospecificity. With the stereospecificity transformation of the active species from low to high, TBIR copolymers with crystalline TPB and TPI blocks and copolymers with TPI blocks are successively formed.

Highly renewable, thermoplastic tetrapolyesters based on hydroquinone,p‐hydroxybenzoic acid or its derivatives, phloretic acid, and dodecanedioic acid

ABSTRACTA series of tetrapolyesters were obtained by polymerizing phloretic acid, hydroquinone,p‐hydroxybenzoic acid, or its derivatives, that is, vanillic acid or syringic acid, and dodecanedioic acid. Each monomer was polymerized in its acetylated form, except for the diacid to undergo polymerization by acidolysis. Initial polymerizations had shown that the use of phloretic acid resulted in better polymer properties than withp‐coumaric acid. The predominantly renewable polymers were obtained by melt polymerization using a two‐stage condensation process whereby antimony(III) oxide was applied as catalyst. Monomer conversions were typically close to 90%.1H and13C NMR, DSC, TGA, solution viscometry, and GPC were applied, as well as polarized microscopy to determine polymer microstructure and composition, transition temperatures, decomposition temperatures, intrinsic viscosities, and other molecular weight properties, and when applicable the liquid crystalline behavior of the polymers. All peaks, including end group peaks in the13C NMR spectra were assigned, the monomer sequence distribution was verified to be random, and a complete dyad analysis involving nine dyads and eight peaks was performed. By usingp‐hydroxybenzoic acid and its derivatives without any, one or two methoxy groups and varying the copolymer compositions, melting temperatures could be tuned between 106 and 181 °C. The tetrapolyesters, which included residues ofp‐hydroxybenzoic acid, formed nematic liquid crystals. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2018,56, 1498–1507