The influence of (macro) monomer functionality on reactivity in radical (co)polymerization

Short-chain polyester methacrylate macromonomers with alkyl, tertiary amine, carboxyl, and hydroxyl end-group functionalities have been synthesized by ring-opening polymerization and subsequent modification. The functionality controlled in the synthesis is imparted onto the comb-polymer structures formed via radical polymerization, with an even greater diversity of materials accessible through copolymerization. This presentation will provide an overview of the materials produced and their applications, which range from degradable cationic flocculants for treatment of oil sands tailings to nanoparticles with tunable biodegradability for drug delivery. Please download the file below for full content

Distribution of functional groups in starved-feed semi-batch free radical copolymerization: An accelerated stochastic modeling approach

Maintaining the quality and cost-efficiency of industrialized materials often requires tradeoffs. For instance, while the majority of chains must be functionalized for end-use applications, there is also a desire to minimize the fraction of functional monomer used in the production of low molecular-weight resins for solvent-borne coatings. To address these questions, kinetic models must not only predict the overall copolymer composition and reaction rates but describe how the reactive groups are distributed as a function of polymer chain-length. In this work, a Kinetic Monte Carlo (KMC) approach is taken to construct a radical copolymerization model. While KMC provides a suitable description of the explicit sequence of chains, the time-consuming computational calculations often hinder the utilization of the method. It is shown that application of scaling methods introduced by Gao et al.1 combined with optimization of the information storage described by Chaffey-Millar et al.2 decreases drastically the computational time to a few minutes (i.e., ~40 times faster). Therefore, this approach allows computation of the complete copolymer composition distribution along with standard model output (average MWs and monomer concentration profiles) in a time not much greater than that required by a deterministic model, providing a solid foundation for optimization of the desired population of polymer chains under industrial conditions. The improved solution of the KMC is demonstrated through consideration of a previously published example of the radical copolymerization of glycidyl methacrylate (GMA) and butyl methacrylate (BMA) in which the average number of GMA units per chain is unity;3 as shown in Figure 1, the accelerated model provides the same accuracy in a fraction of the simulation time. In addition, the influence of methacrylate depropagation will be shown through the application of the model to the high-temperature copolymerization of BMA with 2-hydroxyethyl acrylate in a starved-feed semi-batch reactor. Please click Additional Files below to see the full abstract

Synthesis and utilization of low dispersity acrylic macromonomer as dispersant for non-aqueous dispersion polymerization

Non-aqueous poly(acrylic) dispersions (NADs) used in automotive coating formulations are heterogeneous high-solids suspension of polymeric nano-size particles (\u3c 200 nm) produced by radical polymerization in organic hydrocarbon medium. An important component of the system is the low molecular weight (MW) reactive polymeric dispersant (5000-6000 Da) that stabilizes the particles formed. A vinyl-terminated butyl methacrylate (BMA) macromonomer dispersant synthesized by cobalt chain transfer polymerization (CCTP) has been shown to be more effective at stabilizing the nanoparticles formed during the NAD process than a BMA based grafted dispersant with vinyl groups attached at random positions along the backbone.[1] The macromonomer, although having controlled double-bond placement through CCT chemistry, still have a molecular weight dispersity of close to two (Figure 1A). While the role of dispersity of a self-assembling amphiphilic block copolymer has been studied in emulsion polymerization,[2] no such study exists for dispersion polymerization, which commences as a homogeneous solution. Please click Additional Files below to see the full abstrac

Effect of functional groups and ionization on the radical copolymerization of acrylic acid and cationic monomers in aqueous solution

The use of specialized experimental techniques has been instrumental in developing an improved understanding of aqueous-phase radical polymerization kinetics of industrially relevant water-soluble polymers. In-situ NMR technique allows for reliable data collection at monomer concentrations up to 40 wt%, following both overall monomer conversions as well as composition drift in a copolymerization system. Our work focuses on the kinetics of [2-(methacryloyloxy)ethyl]trimethylammonium chloride (TMAEMC) and 3-(methacryloylamino)propyl]trimethylammonium chloride (MAPTAC), cationic monomers containing an ester and amide functional groups, respectively, copolymerized with both non-ionized (AA) and fully-ionized (NaA) acrylic acid to form copolymers with applications as cationic flocculating agents in water treatment. The drift in monomer composition was found to be almost entirely independent of AA ionization for both TMAEMC and MAPTAC systems, with the cationic monomers preferentially incorporated when copolymerized with AA and NaA up to 80% and 50% molar fraction of TMAEMC and MAPTAC, respectively, (as shown in Fig. 1). Above these compositions, AA (or NaA) was preferentially incorporated, with the azeotrope behaviour dependent on the total monomer concentration in the aqueous solution. The differences in copolymerization behaviour could be attributed to the influence of the functional groups on hydrogen bonding in the aqueous phase. In addition, the apparent system reactivity ratios in both systems were found to be influenced by electrostatic interactions, and thus both initial monomer content and composition. Please click Additional Files below to see the full abstract

Effect of reaction conditions on the distribution of hydroxyl functional groups in HEA- BMA copolymer

Non-functional monomer feedstocks containing alkyl meth(acrylate) components such as butyl acrylate (BA) and butyl methacrylate (BMA) have been replaced or augmented with functional monomers such as 2-hydroxyethyl methacrylate (HEMA) and 2-hydroxyethyl acrylate (HEA) to produce reactive polymer chains of lowered molecular weight (MW) for application in solvent-borne automotive coatings. The polar and functional reactants affects the radical copolymerization kinetics and introduces solvent dependencies.[1] A series of BMA/HEA experiments have been performed at 138 °C to determine the influence of these changing kinetic parameters under starved-feed semi-batch operating conditions. A comparison with BMA/BA copolymerization shows that the influence of hydrogen bonding is small, with the semi-batch system well controlled to HEA contents of up to 50 wt%. Thus, the experiments are well represented by a comprehensive generalized copolymerization model formulated in PREDICI® that considers relevant methacrylate and acrylate side-reactions and uses the chain growth parameters measured in previous kinetic investigations.[2] As well as controlling overall copolymer composition, understanding the distribution of the hydroxyl functional groups among the polymer chains is of importance, as non-functionalized lower-MW chains will not crosslink into the polymer network formed upon application of the coating. A series of BMA/HEA copolymers containing 6.25, 12.5 and 25 wt% HEA were synthesized with weight-average polymer MWs varied between 3000-10000 Da through manipulation of reaction temperature (138 and 160 °C) and initiator loading (2 to 4 mol% relative to monomer) during starved-feed semi-batch operation; at the higher temperature the influence of BMA depropagation becomes more apparent. The amount of non-functional material in the samples is experimentally determined by solvent extraction after forming a crosslinked film, and MWs and HEA contents of the extractable fractions are measured. These experimental results will be compared with predictions from the PREDICI® model as well as a kinetic Monte Carlo representation that calculates how the reactive groups are distributed as a function of polymer chain-length. [1] J. E. S. Schier, R. A. Hutchinson, “The influence of hydrogen bonding on radical chain-growth parameters for butyl methacrylate/2-hydroxyethyl acrylate solution copolymerization”, Polym. Chem. 2016, 7, 4567-4574. [2] J. E. S. Schier, M. Zhang, M. C. Grady, R. A. Hutchinson, “Modeling of Semi-batch Solution Radical Copolymerization of Butyl Methacrylate and 2-Hydroxyethyl Acrylate”, Macromol. React. Eng.. 2018, submitted

Structure modifications of hydrolytically degradable polymer flocculant for improved water recovery from mature fine tailings

Oil sands mining operations in Canada produce large volumes of waste tailings that are difficult to dewater using commercial polyacrylamide-based flocculants. Recently, we have developed a novel hydrolytically-degradable polymer synthesized through micellar radical polymerization of short-chain polyester cationic macromonomers. Poly(PCL2ChMA), made of polycaprolactone choline iodide ester methacrylate with two polyester units, effectively treated mature fine tailings (MFT) solutions as evaluated by measuring initial settling rate, supernatant turbidity, and capillary suction time (CST) of the sediments[1]. Please download the file below for full content

Superabsorbent hydrogels made from bio-sourced butyrolactone monomer in aqueous solution

A new water-soluble monomer, sodium 4-hydroxy-4-methyl-2-methylene butanoate (SHMeMB), formed by saponification of the bio-derived monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL), was copolymerized with acrylamide (AM) in aqueous solution to make superabsorbent hydrogels with equilibrium degree of swelling in the range of 6700–59 000%, depending on monomer ratio and crosslink density. Mechanical strength and storage and loss moduli of the hydrogels were tunable over a wide range through adjustment of the comonomer composition and the crosslinker content. Monomer reactivity ratios of rSHMeMB = 0.12–0.17 and rAM = 0.95–1.10 were determined using copolymer compositions measured at low monomer conversion as well as by applying the integrated form of the Mayo-Lewis equation to fit the drift in comonomer composition with conversion. The reactivity of the SHMeMB : AM system was lower than that of the previously-studied SHMB : AM system, with sodium 4-hydroxy-2-methylene butanoate (SHMB) derived from a similar renewable monomer, α-methylene-γ-butyrolactone (MBL). The differences in reactivity were studied by pulsed laser polymerization coupled with size exclusion chromatography; the comonomer-averaged propagation rate coefficient of the SHMB : AM system was found to be more than double that of SHMeMB : AM, with first estimates for the SHMeMB and SHMB homopropagation rate coefficients of 25 and 165 L mol−1 s−1, respectively, at 60 °C. Despite its lower reactivity, SHMeMB offers advantages over SHMB due to its availability and as superior overall properties of the final hydrogels were achieved.European Regional Development Fund through project POLYFRIEND, within Hungary-Slovakia Cross-border Co-operation Programme [HUSK 1101/1.2.1/0209]; Slovak Academic Information Agency (SAIA) [VEGA 2/0158/17]; Natural Sciences and Engineering Research Council of Canada (NSERC

Update and critical reanalysis of IUPAC benchmark propagation rate coefficient data

The dataset used to generate IUPAC benchmark Arrhenius parameters for propagation rate coefficients in radical polymerization is extended and reanalyzed, taking into account systematic interlaboratory variation

Searching for psychosis: INTREPID (1): systems for detecting untreated and first-episode cases of psychosis in diverse settings.

PURPOSE: Our understanding of psychotic disorders is largely based on studies conducted in North America, Europe and Australasia. Few methodologically robust and comparable studies have been carried out in other settings. INTREPID is a programme of research on psychoses in India, Nigeria, and Trinidad. As a platform for INTREPID, we sought to establish comprehensive systems for detecting representative samples of cases of psychosis by mapping and seeking to engage all professional and folk (traditional) providers and potential key informants in defined catchment areas. METHOD: We used a combination of official sources, local knowledge of principal investigators, and snowballing techniques. RESULTS: The structure of the mental health systems in each catchment area was similar, but the content (i.e., type, extent, and nature) differed. Tunapuna-Piarco (Trinidad), for example, has the most comprehensive and accessible professional services. By contrast, Ibadan (Nigeria) has the most extensive folk (traditional) sector. We identified and engaged in our detection system-(a) all professional mental health services in each site (in- and outpatient services-Chengalpet, 6; Ibadan, 3; Trinidad, 5); (b) a wide range of folk providers (Chengalpet, 3 major healing sites; Ibadan, 19 healers; Trinidad: 12 healers); and c) a number of key informants, depending on need (Chengalpet, 361; Ibadan, 54; Trinidad, 1). CONCLUSIONS: Marked differences in mental health systems in each catchment area illustrate the necessity of developing tailored systems for the detection of representative samples of cases with untreated and first-episode psychosis as a basis for robust, comparative epidemiological studies

Chemical data evaluation: General considerations and approaches for IUPAC projects and the chemistry community (IUPAC Technical Report)

The International Union of Pure and Applied Chemistry has a long tradition of supporting the compilation of chemical data and their evaluation through direct projects, nomenclature and terminology work, and partnerships with international scientific bodies, government agencies, and other organizations. The IUPAC Interdivisional Subcommittee on Critical Evaluation of Data has been established to provide guidance on issues related to the evaluation of chemical data. In this first report, we define the general principles of the evaluation of scientific data and describe best practices and approaches to data evaluation in chemistryinfo:eu-repo/semantics/publishedVersio