Polymer Structure Type Research Articles

Ultrafast synthesis of dialkyne-functionalized polythioether and post-polymerization modification via click chemistry

Herein, we prepare a polythioether with double “clickable” alkyne groups in each repeating unit via an extremely rapid polymerization method and combine it with Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” reaction to construct new topological polymers. A monomer having both electron-deficient and electron-rich dual alkyne functionalities was synthesized and subsequently reacted with 1,6-hexanedithiol (HDT) using 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) as a catalyst, and the reaction proceeded at room temperature for 1 min to give polythioether P1. The obtained polymer was then used as a polymer platform and reacted with a variety of azide compounds to modify the pendant alkynes via CuAAC reaction. The post-polymerization modification (PPM) studies have also been shown to be rapid as the reactions reached completion in 1 h. All synthesized polymers were analyzed using various spectroscopic methods and the results confirmed that quantitative “click” reaction efficiency was achieved in each reaction. It is believed the presented strategy not only provides a time-saving approach for both polymer synthesis and PPM, but also brings a new insight to impart the desired functionalities to a polymer chain with CuAAC “click” chemistry. Thus, a new type of polymer structure that can be prepared rapidly and undergoes fast PPM has been introduced to polymer chemistry with this study. • A Polythioether with clickable pendant units has been synthesized extremely rapidly in 1 min. • Post-polymerization modification (PPM) via Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) “click” reaction has been successfully carried out. • Quantitative “click” reaction efficiency has been achieved in all cases. • Time- and energy-saving polymerization and PPM method have been developed.

Ring-Opening Copolymerizaton of Cyclohexene Oxide and Succinic Anhydride by Zinc and Magnesium Schiff-Base Complexes Containing Alkoxy Side Arms

The ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides is a promising method for the synthesis of new polyesters with various polymer properties. Among previously reported metal catalysts for ROCOP, the Schiff-base complexes have gained significant attention because of their ease of synthesis and modification. In this work, zinc and magnesium complexes containing Schiff-base ligands with different alkoxy side arms [-(CH2)2O- and -(CH2)3O-] were synthesized and shown to have a cubane metal core by X-ray crystal structures. All complexes were studied in the ROCOP of cyclohexene oxide (CHO) and succinic anhydride (SA) in toluene at 110 °C. The zinc complex having a shorter side arm is the most active catalyst for copolymerization, giving poly(CHO-alt-SA) with narrow dispersity and negligible ether linkage. On the other hand, magnesium complexes were not active because of the formation of stable carboxylate species. The detailed analysis of polyester obtained from zinc complexes unexpectedly revealed three different types of polymer structures occurring at different polymerization times. Cyclic polymer was generated at the beginning by intramolecular transesterification of the alkoxy side arm, giving a low-molecular-weight polyester. At higher conversion, cyclization diminished, giving just a linear polyester but with minor competitive formation of higher-molecular-weight polyester having cyclohexanediol as an end group. On the basis of a thorough understanding of the polymerization mechanism, the desired cyclic poly(CHO-alt-SA) was successfully synthesized using a low monomer/catalyst ratio.

Thermodynamic Properties of Poly-1H,1H,5H-octafluoropentyl Acrylate

The temperature dependence of heat capacity of the amorphous poly-1H,1H,5H-octafluoropentyl acrylate between T = (6 and 350) K was measured by a adiabatic calorimeter. In the interval 225 K to 242 K the glass transition was detected and this thermodynamic parameters were determined. On the basis of the experimental data, the standard thermodynamic functions, namely, the heat capacity, enthalpy, entropy and Gibbs function of heating were calculated for the polymer in the interval from T → 0 K to 350 K. The low-temperature (T < 50 K) dependence of the heat capacity was used to evaluate the topology’s type of polymer structure.

Morphological study on the reactivity of styrene‐divinylbenzene copolymers in a chloromethylation reaction

AbstractStyrene‐divinylbenzene (S‐DVB) copolymers with different kinds of porous structures were synthesized by aqueous suspension polymerization using n‐heptane as the pore forming agent. The amount of this solvent (monomer dilution degree) and the DVB content in the organic phase were varied. The combination of three different dilution degree values and three DVB contents yielded three series of copolymers with a variety of porous structures. The three series were composed by copolymers with pore diameters (D) in the following ranges: D &lt; 500 Å, 500 &lt; D &lt; 1000 Å, and D &gt; 1000 Å, respectively. The effect of synthesis conditions on the pore size distribution and on the copolymer matrix rigidity was evaluated. These copolymers were submitted to a chloromethylation reaction with a paraformaldehyde/gaseous HCl mixture in the presence of zinc chloride as a Lewis acid catalyst and 1,2‐dichloroethane as solvent. The effect of the copolymer porosity on the chloromethylation reaction extension was evaluated. It was possible to observe that a gel copolymer with a high swelling capacity in the reaction medium achieved the same chloromethylation yield observed for a high porous copolymer. This result thus indicates that, in the case of the chloromethylation reaction studied here, the high swelling capacity of the gel copolymer can counterbalance its limited surface area, turning this type of polymer structure as reactive as a macroporous one. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of Hollow-Structured Nano- and Microspheres from Pectin in a Nanodroplet Emulsion

Hollow-structured nano- and microspheres with diameters ranging from 24 microm to 160 nm were successfully produced from chemically modified pectin (Ma-Pec) through a two-step synthesis. In a first step, the Pec was modified with glycidyl methacrylate (GMA) in a heterogeneous phase system, indeed consisting of water-soluble Pec and water-insoluble GMA, via an interfacial reaction at the interface of the GMA-water phase system after 12 h under continuous stirring of 1000 rpm at 60 degrees C. In a second step, the spheres were prepared in a water-in-benzyl alcohol nanodroplet emulsion at 12000 rpm under a bubbling stream of nitrogen in the presence of sodium persulfate, as initiator, and TEMED, as catalytic agent. FT-IR spectra revealed that the vinyl groups (CC) coming from the GMA were attached onto backbone of the polysaccharide. 13C-CP/MAS NMR spectra demonstrated that the spheres were formed via carbon-carbon pi-bonds on Ma-Pec in the water phase, for the duration of the dispersion stage. The dark center (an empty core) and edge of the hollow spheres could be easily identified by SEM micrographs. This type of polymer structure represents a class of unique material with particular importance in terms of state-of the-art applications in both nano- and microencapsulation of drugs, for example, protection shields of biologically active agents.

Improved dewaterability of iron oxide dispersions: the role of polymeric flocculant type, pH and shear

AbstractSubstantial amounts of recyclable water are trapped in mineral waste tailings dams annually due to less than effective dewatering processes. To address this, a study has been conducted of the flocculation performance of four high molecular weight (&gt;5 × 106 Da) polyacrylamides, non‐ionic homopolymer (PAM N), anionic carboxylate substituted copolymer (PAM A), anionic sulfonate substituted copolymer (PAM S), and cationic trimethyl amino ethyl substituted copolymer (PAM C), on the dewaterability of iron oxide suspensions as a function of pH. Significant polymer structure‐mediated and pH‐dependent trends were observed.Upon flocculation with up to 500 g polymer/t solid, settling rates in the range of 3–100 m/h were observed, along with sediment solid loading in the range 35–40 wt%. Settling rates varied depending on polymeric flocculant type, and were higher for anionic and cationic polymers than for non‐ionic polymers. Settling was most efficient at and below the iso‐electric point (iep, pH 8.5). Polymer structure type did not have any noticeable impact on the extent of pulp consolidation. Moderate shear significantly improved the consolidation (55 wt% solid) of pre‐sedimented pulps. For the selection of a flocculant, a polymer that displayed an opposite charge to that of the particles appeared to provide improved flocculation and dewatering performance. Copyright © 2008 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Construction of Supramolecular Complexes by Use of Planar Bis(β-diketonato)cobalt(II) Complexes as Building Blocks

Abstract As building blocks for the construction of supramolecular complexes, two bis(β-diketonato) CoII complexes were examined. From the self assembly of each CoII complex and a polypyridyl ligand, 2′,4′,6′-tri(4-pyridyl)pyridine, two types of polymer structures, 1D zigzag chain and 2D hexagonal net, were obtained.

Enhanced flocculation and dewatering of clay mineral dispersions

Results emerging from the several studies recently performed to provide fundamental understanding of the interplay between mineral pulp chemistry, flocculation performance, particle interactions, role of applied shear and dewaterability of model colloidal kaolinite and smectite dispersions are presented and discussed. Beneficial links between pulp interfacial chemistry (particle zeta potential), particle interactions (shear yield stress) and beneficial dewatering behaviour (batch settling rate and sediment solid loading), established through the influence of hydrolyzable metal ions, pH, temperature, high molecular weight polymer structure type (anionic polyacrylamide vs non-ionic polyethylene oxide) and shear, are shown. The application of the findings and new knowledge gained for a marked improvement in clay pulp dewaterability is discussed.

The effect of polymer structure type, pH and shear on the interfacial chemistry, rheology and dewaterability of model iron oxide dispersions

The effect of high molecular weight (7.5–9 × 10 6 Da) polyacrylamide flocculant structure type (anionic polyacrylamide, PAM A and non-ionic polyacrylamide, PAM N) on the interfacial chemistry, rheology and dewaterability of a colloidal iron oxide dispersion has been investigated at three pH values where the particles are at the isoelectric point (iep) and either side of the iep. PAM A was found to adsorb with a lower affinity than PAM N at all pH values tested, however, PAM A had a more significant effect on the particle zeta potential and the shear yield stress. Highest settling rates (100 m/h) were achieved with PAM A at pH values at and below the iep, with flocculant dosage below 100 g polymer/t solid. Settling rates with PAM N at similar concentrations, however, only produced settling rates between 5 and 10 m/h. Pulp pH and the addition of the flocculants (up to 500 g polymer/t solid) had no noticeable effect on the extent of the pulp consolidation. Significantly, shear of pre-sedimented dispersions was found to increase the consolidation by up to 15 wt%. Polymer structure type was found to have a significant effect on the rheology of the dispersion, with PAM A-flocculated dispersions leading to a higher yield stress than dewatering with PAM N.

Synthesis, characterization and evaluation of sulfonic resins as catalysts

Ion-exchange resins have been often used as catalysts especially those based on styrene–divinylbenzene copolymers with sulfonic acid groups in the aromatic rings of polymer chains. That is due to the advantages of heterogenous catalysis over the homogeneous acid catalysis. Moreover, resin catalysts can often lead to high selectivity in organic reactions due to the matrix effects. Therefore, the study of copolymers synthesis conditions to determine the type of polymer structure produced as well as the characterization of sulfonic resins obtained thereof are of great interest. The current paper describes the synthesis, characterization and evaluation as catalysts of sulfonic resins derived from polymer supports synthesized by aqueous suspension polymerization of styrene and divinylbenzene. The reaction conditions were varied and polymer supports with different physical properties and morphological characteristics were obtained. The polymer supports were chemically modified by sulfonation. The resultant sulfonic resins had their catalyst activity evaluated in the esterification of acetic acid with n-butanol.

Flocculation and dewatering behaviour of smectite dispersions: effect of polymer structure type

In this study, the influence of polymer structure type on the flocculation and dewatering behaviour of smectite clay dispersions has been investigated. Anionic polyacrylamide–acrylate copolymer (PAM) and non-ionic polyethylene oxide (PEO) polymer adsorption onto smectite particles, in the presence of 5 × 10 −2 M Ca(II) ions, led to polymer structure dependent modifications in surface chemistry, shear yield stress, settling rates and consolidation behaviour. The magnitude of the particle zeta potential decreased with increasing flocculant concentration for both polymers but was significantly greater for PEO than PAM. Polymer adsorption studies showed that PEO displayed a higher affinity and greater adsorbed density than PAM, consistent with the zeta potential data. An optimum flocculant dosage for an enhanced flocculation performance was observed at 500 g polymer/ton solid, where less than 50% the plateau adsorbed amount for both polymers occurred. The magnitude of the shear yield stress was strongly dependent upon the polymer structure and concentration. PEO produced greater particle interactions and more strongly networked flocs, reflecting higher shear yield stress than PAM. Significant improvement in the dewatering rate was observed in the presence of PEO in comparison with PAM, at similar polymer concentration. Furthermore PEO flocculated dispersions showed dramatic improvement in consolidation upon shear whilst PAM produced no such effect. A strong correlation between the polymer structure type and flocculation performance, floc shear-sensitivity and the dewatering behaviour of smectite dispersions was established.

Temperature influence of nonionic polyethylene oxide and anionic polyacrylamide on flocculation and dewatering behavior of kaolinite dispersions

Nonionic polyethylene oxide (PEO) and anionic polyacrylamide (PAM) flocculation of kaolinite dispersions has been investigated at pH 7.5 in the temperature range 20–60 °C. The surface chemistry (zeta potential), particle interactions (shear yield stress), and dewatering behavior were also examined. An increase in the magnitude of zeta potential of kaolinite particles, in the absence of flocculant and at a fixed PEO and PAM concentration, with increasing temperature was observed. The zeta potential behavior of the flocculated particles indicated a decrease in the adsorbed polymer layer thickness, while at the same time, however, the adsorbed polymer density showed a significant increase with increasing temperature. These results suggest that polymer adsorption was accompanied by temperature-influenced conformation changes. The hydrodynamic diameter and supernatant solution viscosity of both polymers decreased with increasing temperature, consistent with a change in polymer–solvent interactions and conformation, prior to adsorption. The analysis of the free energy (Δ G ads) of adsorption showed a strong temperature dependence and the adsorption process to be more entropically than enthalpically driven. The polymer conformation change and increased negative charge at the kaolinite particle surface with increasing temperature resulted in decreased polymer bridging and flocculation performance. Consequently, the shear yield stress and the rate and the extent of dewatering (consolidation) of the pulp decreased significantly at higher temperatures (>40 °C). The temperature effect was more pronounced in the presence of PEO than PAM, with 40 and 20 °C indicated as the optima for enhanced performance of the latter and former flocculants, respectively. The results demonstrate that a temperature-induced conformation change, together with polymer structure type, plays an important role in flocculation and dewatering behavior of kaolinite dispersions.

Investigation of the effect of polymer structure type on flocculation, rheology and dewatering behaviour of kaolinite dispersions

The influence of an anionic polyacrylamide–acrylate copolymer (PAM) and a nonionic polyethylene oxide (PEO) polymer on the surface chemistry, shear yield stress, settling rates and consolidation behaviour of kaolinite dispersions has been investigated at pH 7.5. The magnitude of the particle zeta potential decreased with increasing flocculant concentration for both flocculants but was much greater for PEO, due to an increased adsorbed layer thickness compared with PAM. Furthermore, the adsorption studies showed a higher affinity for PEO than PAM. The optimum flocculation for improved clarification rate occurred at less than half the plateau adsorbed amount for both polymers. At similar polymer concentrations, the kaolinite floc sizes were larger and the settling rates greater in the presence of PEO than PAM. Upon shear, the consolidation of pre-sedimented kaolinite slurries significantly improved under flocculation with PEO, while PAM produced no such effect. The magnitude of yield stress was strongly dependent upon the polymer structure, with greater yield stress (stronger interparticle bridging forces) observed for PEO than for PAM flocs. The difference in shear sensitivity of the flocculated slurries may be attributed to polymer structure-related adsorption and interfacial conformation behaviour. PEO polymer chains adsorb via hydrogen bonding interactions between the ether oxygen (Lewis base) and OH groups (Bronsted acid) associated with aluminol and silanol groups, which led to flexible and compressible floc structures. For PAM, however, although the adsorption is still via hydrogen bonding between the silanol and aluminol OH groups at the particle surface and the polymer's primary amide functional groups, the interactions appear to be weakened as a consequence of electrostatic repulsion between the polymer's COO − pendant groups and the negatively charged kaolinite surface. This, in conjunction with possible steric hindrance due to PAM polymer chain branching, led to the formation of loose, open and fragile flocs. A strong correlation between the polymer structure type and flocculation, shear sensitivity and the dewatering behaviour of kaolinite dispersion was established.

Flow microcalorimetry and competitive liquid sorption: II. Liquid sorption and wetting on macroreticular hydrophilic/hydrophobic networks

Three different types of polymer networks (polymer resins) were investigated by flow microcalorimetry and selective liquid sorption from 1-propanol(1)-water(2) mixtures. Type 1 network structure is formed by non-polar, non-swelling, macroporous resins (Amberlite XAD-2, Amberlite XAD-4). The composite isotherms for alcohol sorption were S-shaped. 1-Propanol is preferentially sorbed up to x1≈0.5. Macroreticular non-ionic resins, Amberlite XAD-7 and XAD-8, represent the second type of polymer structure. These particles have a considerable extent of swelling in the binary liquid mixture and 1-propanol was preferentially sorbed by the polymer. The composite isotherms were U-shaped and exhibit maxima and minima. The third type of network structure is attached to macroreticular polar, hydrophilic ion-exchange resins (Chelite-S, Amberlyste A-21). Depending on the composition range of the binary liquid mixture, the resins may swell to a different extent and water is preferentially embeded in the porous polymer network. The swelling of the polymer networks was monitored by the gravimetric technique in seperate experiments. The sorption capacity determined from the liquid uptake of the resins was related to the sorption capacity derived from the reduced surface excess. The enthalpy effect accompanying the sorption process was determined by flow and immersion microcalorimetry. The enthalpy of displacement isotherms reveals differences in polarity and swelling ability of the polymer network fairly well. Structural changes in the adsorption layers and formation of alcohol–water clusters on the surfaces play an important role.

SYNTHESIS OF POLYMER STRUCTURES FROM LIGNOCELLULOSE FEEDSTOCKS

Two types of polymer structures were synthesized from feedstocks derived from mesquite wood. One appears to be a random copolymer with styrene which was polymerized by free radical mechanisms in a water suspension. As much as 10% by weight of the mesquite feedstock was added to the copolymer structure. This addition raised the Tg of the copolymer by 10°C over that of the polystyrene homopolymer. The second polymer structure was a modified adhesive resin. In this case, the mesquite wood feedstock was reacted with paraformaldehyde by condensation to a B stage. Particle boards containing 55 parts of ground mesquite to 45 parts of adhesive resin were compression molded for test purposes. As had been demonstrated by earlier investigators, the use of paraformaldehyde was required to bridge the substituted aromatic structures derived from the mesquite lignin. It was concluded that substantial fractions of lignin recovered from biomass could be utilized in the synthesis of high molecular weight polymers. The majo...

Base pairing in 5-chlorouridine.

5-Chlorouridine has been found to crystallize from water with the molecules of the nucleoside arranged in a base-paired, parallel-stranded ribbon. This type of polymer structure has not been previously considered for nucleic acids. We have constructed a model of polyuridylic acid based upon the 5-chlorouridine crystal structure and wish to suggest it as a plausible molecular complex for this and perhaps other polynucleotides.The crystals are monoclinic, space group P2(1), with a = 7.536 A,b = 5.790 A, c = 13.219 A, and beta = 99.89 degrees . There are two 5-chlorouridine molecules per cell. The nucleoside bases are linked across a 2(1) axis with hydrogen bonds between N(3) and O(4). The hydrogen bond length is 2.85 A. The conformation of the base with the ribose about the beta-glycosidic bond is anti, with a torsion angle relative to O (1') of -59.8 degrees . The sugar puckering is C(2')-endo, and the conformation about the C(4')-C(5') bond is gauche-gauche. To build the polymer model, the C(4')-C(5') bond was rotated 100 degrees and the sugar-base torsion angle adjusted to -30 degrees . This brought O(3') and O(5') of adjacent sugars close enough to make the phosphate ester linkage found in polynucleotides.

Carborane polymers. IV. Polysiloxanes

AbstractCarboranes attached to silicon through straight‐chain alkyl groups were prepared and characterized for thermal stability by TGA and molecular weight change on heating. The monomers for these polymers were prepared generally by platinum‐catalyzed addition of a silylhydride to an alkenyl or dialkenyl carborane. Polymerization was effected by hydrolysis‐condensation of chlorosilanes, ring opening of cyclosiloxanes, and condensation of alkoxy and chlorosilanes. Two types of polymer structures were prepared, one contained m‐carborane in the chain backbone, the other contained o‐carborane as pendant alkylcarborane groups. Both types were obtained as elastomers; however, higher proportions of carborane in the polymers reduced elasticity and finally resulted in nonelastomers. TGA of the backbone carborane siloxane polymer indicated degradation at 370°C. in nitrogen and at 235°C. in air. Chain scission, as determined by molecular weight decrease, was observed on heating in nitrogen at 350°C. TGA of the pendant carborane siloxane polymer indicated that degradation in nitrogen and in air occurred at greater than 400°C. However, chain scission, as determined by molecular weight decrease, was observed upon heating at 300°C. in nitrogen.