#polyelectrolytes

How Polyelectrolytes Improve Wastewater Treatment Efficiency

Abstract

Significant research and developments are taking place in the field of synthetic polyamides (Nylons). One of the most investigated members of this family of polymers is poly (ε-caprolactam) (PCL, Polyamide 6, PA6, Nylon 6). Herein, a brief overview will be presented on the major recent advancements in the anionic ringopening polymerization (AROP) of ε-caprolactam (CL) by the initiating combinations of metal lactamates and carbamoylcaprolactams and by some other initiating systems, e.g. protected N-heterocyclic carbenes , NaHMDI and σ-borane-barium complexes. The in situ polymerization of CL in the presence of additives, such as flame retardants, reinforcing agents and fillers, is also discussed. Examples are presented on the determination of the molecular weight distributions (MWD) and average molecular weights of Polyamide 6 by GPC (SEC) measurements with 1,1,1-trifluoroethanol as eluent used routinely in our laboratories. Finally, a glimpse will be provided into the ongoing intensive research related to thermoplastic resin transfer molding (T-RTM) processes aiming at producing Polyamide 6 products, such as reinforced PA6 and composites, by rapid in situ polymerization of CL.

Keywords:Polyamide 6; Nylon 6; ε-Caprolactam; Anionic ROP; Initiator; Activator; PA 6 additives; GPC (SEC); Thermoplastic Resin Transfer Moulding (T-RTM)

Introduction

Synthetic polyamides (Nylons) are still among the most important macromolecular materials with a wide variety of useful properties and applications even after nine decades of their discovery [1]. Significant research and developments are taking place with these polymers worldwide. These include exploring new polymerization chemistries for their production, modification of their structure and properties, and finding new ways of processing, especially by thermoplastic resin transfer molding (T-RTM), for a large variety of composites and products. In this brief overview, we attempt to provide a glimpse into the recent major advancement with one of the members of the Nylon family, Nylon 6 (Polyamide 6, PA6).

Polymerization of ε-Caprolactam: Effect of Catalysts, Additives, Fillers and Reinforcing Materials

Beyond doubt, poly (ε-caprolactam) (i.e. Polyamide 6, PA6, Nylon 6) is one of the most widely investigated polymers due to its versatile properties and broad application possibilities. Polyamide 6 is mainly made by the anionic ring-opening polymerization (AROP) of ε-caprolactam (CL). The major current polymerization technologies are based on the AROP of CL by initiator-activator combinations [2-5]. The most widely used initiator-activator initiating systems include metal lactames (e.g. Na-, K-, Mg-lactames) in conjunction with carbamoylcaprolactams (CCL) such as hexamethylene-1,6-dicarbamoylcaprolactam. The major mechanistic steps of the polymerization of CL by such initiating systems are displayed in Scheme 1. One of the main advantages of this polymerization reaction is related to the fact that it can be carried out by bulk polymerization in the molten state of CL and the components of the initiating system, i.e. initiator and activator, to high yields without significant induction period at elevated temperatures. This solventless process with nearly quantitative monomer conversion without any side product can be considered as one of the most efficient green polymerization processes.

However, it is well-known that AROP is sensitive to moisture, which is able to inhibit the CL polymerization by reacting with either the components of the initiating systems or with the amide anion in the propagating chain [Scheme 1]. Interestingly, the effect of moisture on CL polymerization with industrial initiator and activator combinations has only recently been studied in a systematic manner by Wilhelm et al. [2,3]. They have found by polymerization kinetic investigations that the water present in the polymerization system of CL can be compensated by adding appropriate amounts of initiator and activator. Other systematic investigations on the effect of the condition of CL bulk polymerization with commercially used initiatoractivator mixtures are still lacking, although such studies are of paramount importance for the rapidly developing thermoplastic resin transfer molding (T-RTM) techniques, used for obtaining, in addition to other polymers, Polyamide 6 products as well. In one particular case, Kang and coworkers [4] have recently attempted to determine the optimal polymerization conditions for obtaining carbon fiber reinforced PA6 by TRTM with the use of lactamate-CCL initiating system by varying the injection rate of the components.

Investigations with other than lactamatecarbamoylcaprolactame initiating systmes have also been reported for AROP of CL. Buchmeiser et al. [6,7] carried out CL polymerization with latent, protected Nheterocyclic carbenes, and revealed the catalytic effect of such compounds as a function of the structure of the substituents. Sodium hydride (NaH) in combination with 4,4′-Methylenebis(phenyl isocyanate) (MDI) was used by Kim and coworkers [8] to initiate bulk (melt) CL polymerization to prepare Polyamide 6 composites with multiwalled carbon nanotubes. A complex of barium with σ-borane was successfully applied by Battacharjee et al. [9] to catalyze AROP of CL under mild conditions. Polymerization of CL in the presence of various additives is under intensive investigations nowadays. This can be considered as the major current trend in the field of the chemistry and processing of Polyamide 6, attempting mainly to reach short processing times to obtain advanced composite products, especially by TRTM. The following classes of additives have been recently investigated for the in-situ polymerization of CL by AROP: flame retardants [10-12], fillers, such as titania [13], zinc oxide [14], boron nitride [15] silica [16], montmorillonite [17] and multi-walled carbon nanotubes [8,18,19], and reinforcing agents, like glass fiber [20,21] and carbon fiber [4]. It has to be noted that in spite of its importance usually neither the CL monomer conversion nor the average molecular weights and the molecular weight distribution (MWD) are determined in such instances.

Characterization of Poly(ε-caprolactam) by Gel Permeation Chromatography

Although it is widely known that the MWD and the average molecular weights as well play critical role in the major properties of polymers for both processing and application purposes, it is quite surprising that MWD determinations of Polyamide 6 by GPC (called also size exclusion chromatography, SEC) is rather rare in the open literature. In the few recent instances, GPC of PA6 and CL copolymers has been carried out in solvents like hexafluoroisopropanol (HFIP) [22,23], DMF [24], THF (for low MW PA6) [19] and m-cresol (for CL copolymer) [25]. In the course of our recent investigations on CL polymerization, we have found that 1,1,1trifluorethanol (TFE), as an alternative to HFIP, can also be used effectively as mobile phase in GPC for the determination of the MWD and average MWs of PA6 with a broad range of molecular weights. As displayed in Figure 1, GPC can also be utilized to follow the progress of CL polymerization. In this Figure, the low MW peak, i.e. the peak at higher elution volumes, corresponds to the CL monomer. The gradual disappearance of the monomer peak and simultaneous increase of the polymer peak can definitely be applied to follow the polymerization process in addition to the determination of the MWD and the average MWs of the resulting Polyamide 6. These findings by us indicate that GPC with 1,1,1-trifluoroethanol as eluent can be routinely utilized for not only the determination of the MWD of Polyamide 6 products, but it can also be used to investigate the progress of the polymerization reaction of CL as well.

Polymerization of ε-Caprolactam by Thermoplastic Resin Transfer Moulding (T-RTM) for Obtaining Polyamide 6 and Its Composites

Intensive research and development is taking place worldwide with significant interest and activities in the field of T-RTM for producing the broadest possible range of products based on Polyamide 6 [2,4,21,26]. This is due to the fact that the melt (bulk) polymerization of CL, having low melt viscosity at elevated temperatures, can be carried out in situ in the presence of suitable initiator-activator combinations in a short time. Such a process provides economic and energy saving technological advantages over classical injection molding technologies which preferentially use preformed polymers. T-RTM processing of Polyamide 6 composites has been recently used with a variety of additives, such as reinforcing materials [4,18,19] and fillers [15-17]. However, investigations on the effect of the reaction conditions on the CL conversion and MWD of the resulting Polyamide 6 obtained under T-RTM or similar techniques are very rare. As mentioned earlier, Wendel et al. [2,3] explored the effect of water on the rate and outcome of CL polymerization in a T-RTM process. The optimization of the injection speed in T-RTM of CL by varying the sodium caprolactamate/CCL ratios in the presence of carbon fiber was recently attempted by Kang and coworkers [4]. However, systematic investigations on the effect of the major reaction parameters on the CL bulk (melt) polymerization with industrial reagents is still lacking. Considering this situation, our recent research efforts aim at revealing these correlations, which might be broadly utilized in T-RTM and other in situ bulk polymerization reactions with CL for finding optimal processing conditions [27].

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Abstract

This article will give complete overview on recent development in co-process excipient technology and approaches involved in its development. The co-processed excipients help to overcome deficiencies occurring with use of single general grade excipients. Formulation scientist recognized that the single component excipient cannot always provide the essential performance in manufacturing or formulation to certain active pharmaceutical ingredient (API). Hence attention on the production of multifunctional excipient with improve performance was seen to meet the need of formulation. In order to justify rise in new drug development and also high industrial output demand new combinations of existing excipient were tested for improving excipient functionality. Now days the particle engineering of individual excipient and their combinations by using co-processing technique has provided an attribute tool for developing high functionality excipients to modern drug delivery system. The co-processing is a process with interaction of two or more excipients at sub particle level which turn to provide a synergy of functionality improvement as well as masking the undesirable properties of individual excipients. It is synergistic outcome of the combination of excipients as material property into consideration .The specific excipients are best suited for particular dosage form as a selection criterion for excipients and various excipient interaction. The excipient as like of API need to be stabilized and to be standardized along with safety evaluation parameters. These co-excipients have high functionalities as compared to the individual excipients like better flow property, reduced lubricant sensitivity and compressibility.

Keywords: Excipients; Co-Processing; Particle Engineering; Novel Drug Delivery System

Introduction

In recent year scientists have found that a single excipient cannot always provide the requisite performance to allow the certain API to be manufactured or formulated. The co-processed excipients are combination of two or more compendial or non-compendial excipients which are designed to physically modify their properties in manner that are not achievable by simple physical mixing and without a significant chemical change. Development of the co-processed excipients starts with selection of excipients to be combined, preparation method, their targeted proportion to get optimized product with desired physico-chemical parameters and minimizing avoidance with batch to batch variations. Excipient of a reasonable price has to be combined with optimal amount of functional material in order to obtain the integrated product, with a superior functionality than simple mixture of components. The co-processing is interesting because products are physically modified in special way without altering chemical structure. The fixed and homogenous distribution of components is achieved by embedding then within mini granules. Segregation is diminished by the adhesion of actives on the porous particles making process validation and in process reliable and easy control. Co-processed excipient enhances performance of established excipient that possess performance and improvements: in flow, increased surface area, compaction etc [1-3].

Types of Excipients [2,4-6]

Generally, types of excipients are classified into four types enlisted below:

i. Single chemical entity

ii. Physical mixture or blends of excipients

iii. New chemical entities

iv. Co-processed excipients

i. Single chemical entity

The single entity excipient is nothing, but the primary component used as excipient. It may contain other components like:

a. Concomitant component: is a balance between excipient composition and its functionality. These components should be considered as part of composition profile and hence not be construed as being a undesirable, nor confused with presence of added substance [2].

b. Processing Aids: are chemical substances which are used for specific processing need and benefit in excipient manufacturing process, like to improve chemical and physical process ability, to enhance a chemical synthesis reaction, to provide stabilization during the manufacturing process etc. The processing aids can be removed during the excipient manufacturing process or, depending on process clearance capability; it may remain as low level residual in final excipient. [4,5].

c. Additives: It is defined as any substance not normally consumed as a food by itself and one which is intentionally added to food, or for technical purpose in manufacture, processing, preparation or storage of such food to improve their physico-chemical properties. Normally additives are added by simple mixing process and they are incorporated in amount required to produce intended effect. Additives added not be of official grade, it should be of appropriate quality with safety been evaluated for their proposed use. Hence, the additive does not detrimental impact on excipient function and the final drug product safety/efficacy [5].

ii. Physical mixture or blends of excipients

It is a simple physical mixture or blends of two or more excipients to maintain shear processes where, individual components are mixed together without significant change. For solid mixture the individual excipients remain physically separate at particulate level. Excipient blends can be either solid or liquid after simple mixing typically for short duration [3,4].

iii. Novel excipients or new chemical entities

An excipient used for first time in formulation or by a new route of administration is classified as novel or new according to the ICH Guideline. On the other hand, this guideline defines known excipients that are commonly used and well-established usually included in pharmacopoeias and used in registered drug products. When an excipient has not previously been used in a pharmaceutical formulation then there are a number of conditions set out by the US and European regulatory authorities to allow for its use. They are not fully qualified by existing safety data with respect to currently proposed level of exposure, route of administration or duration of exposure [4,5].

iv. Co processed excipients

It is a combination of two or more compendial or noncompendial excipients that are designed to physically modify properties in such manner not achievable by simple physical mixing without significant chemical change. Various methods are available for co-processing like milling, granulation, melt extrusion, spray drying etc. The choice for the specific method/ technique will depend on the material used and desired physical properties to be achieved. Likewise, ratios of the components may vary depending on target performance to attain [2,5].

History

The key objective for co-processing was to achieve a product with additional value associated to the ratio of its functionality and cost. The aspect that occurs during the co-processing method is not understood absolutely but appears to achieve product components in intimate association with each other as single entity. This association cannot be achieved by simple dry blending but requires appropriate co-processing technique.

Primarily, co-processing concept was implemented in food industry to improve stability, dispersibility, gelling properties of food additives. Few co-processed combinations used were Micro crystalline cellulose (MCC) and galactomanan with glucomannan, MCC with Carboxy methyl cellulose (CMC) and sodium alginate complex.

In pharmaceutical industry, the co-processing concept was established in early 1990 with the introduction of co-processed combinations like MCC and calcium carbonate. Cellactose is a co-processed combination of cellulose and lactose, ProSolv is a combination of MCC and colloidal silicon dioxide [7,8].

Excipients Selection Criteria in Co-Processing

The combination of excipient selected for co-processing should compatible and non-reactive to each other. For example, two hexitol group excipient Mannitol: Sorbitol are co-processed to achieve good compressibility as tablet excipient where first is poorly compressible and less hygroscopic and later is good compressible but highly hygroscopic to create balance between plasticity and brittleness. A few other examples of co-processed excipients studied are combination of Lactose: PVP K30: Starch as a ready to use excipient for tablet with diluents, binder and disintegrant property, MCC: Sodium starch glycolate for direct compression immediate release formulations, Dibasic Calcium Phosphate dihydrate co-processed with Pre gelatinised starch for direct compression with binder and diluents property [9-12].

Regulatory Aspects in Co-Processed Excipient

Excipients combinations through co-processing do not produce any chemical modification in the incorporated excipients. Individual properties of excipient are retaining in the combination, the only novelty is the improved functionality with same physical form. Hence, the co-processed combination does not require any toxicological study and can be considered safe if the parent excipients are declared safe by the regulatory agencies GRAS. Very few co-excipients are described in official monograph like Dispersible Cellulose in B.P., Compressible Sugar in U.S.P/NF. Their non-compendial status is the major hurdle in the success of coprocessed excipient in the market. This obstacle will be overcome in the coming future as with New Excipient Safety Evaluation Procedure (NESEP), and excipients now could be reviewed outside the FDA drug approval process. Affirmative opinion from experts of IPEC team will limit the risk of FDA dismissal of drug based on excipient and could encourage innovation in the pharmaceutical industry [13,14].

Current & Future Status of Co-process excipients

At present co-processed excipients have less applicability in the pharmaceutical industry but surely these will be utilized with enhanced functional properties at low concentration in future. Very few new chemical entities are being introduced in market due to stringent rules and regulations by considering safety, efficacy, and cost. Also, very few improvements in existing excipients will help in increased use of co-processed excipients in coming future. Uprising technologies and many more modification are implementing daily in Pharmaceutical industry to achieve high production rate. A growing popularity of high functionality excipients counterpart tablet machine increasing speed capabilities, to modulate the permeability, solubility, or stability of drug, increasing performance expectations related to disintegration, dissolution, bioavailability etc. makes a fantastic opportunity for the development of novel drug delivery system. Forthcoming novel excipient combinations and new co-processing techniques without any doubt going to attract both in research and pharmaceutical industry [15,16].

Fundamental solid-state properties of excipient

The solid-state properties are characterized by three levels as molecular, particle and bulk. These levels are closely linked with each other, reflecting change in one level with another level shown in (Figure 1). The first molecular level is crystal lattice and include phenomenon such as polymorphism, pseudo polymorphism and amorphous state. The second level consist of individual particle size, shape, porosity, and surface area. The third is bulk level comprises of a group of particles and their physical properties. The individual levels depend over each other which provides framework for the development of novel combination of existing and new grade of excipients. The essential solid-state properties of particles like morphology, size, shape, porosity, density, surface area influence excipient functions such as flowability, dilution, lubrication and disintegrating potential, compressibility and Compatability.

The primary characteristic associated with excipient is that no chemical change occur during co-processing and also the reflected changes showed in the physical properties have to prove that coexcipient do not show any chemical change. There should not be covalent bond formation when these individual ingredients are combined to form co-excipient. Also, stereochemical environment, reorientation, bond breaking and the intermolecular forces responsible for new shapes confirms the formation of a new composition. Analytical techniques for characterization used like particle size distribution, specific surface area, SEM images and X-ray diffractogram (XRD) etc. However, the techniques NMR, HPLC, FTIR, DSC, are used in order to aid control their structural properties [17-19].

Methods Of Coprocessing [20-25]

i. Spray Drying.

ii. Solvent Evaporation.

iii. Crystallization.

iv. Melt Extrusion.

v. Granulation/Agglomeration

i. Spray Drying

This technique is applicable for transformation of feed from fluid state into dried particulate form by spraying the feed into the hot drying chamber. It involves continuous drying operation processing. The feed may be in the form of solution or suspension. The dried product can be obtain in powders, granules or agglomerates depending upon it’s physical and chemical properties, dryer design and final powder properties desired. The spray drying combination of ingredient under solid or dry form during drying, by atomizing active compound in suspension or solution form (Figure 2).

ii. Solvent Evaporation

It involves use of liquid as a vehicle to dissolve excipient in organic solvent in which it is immiscible. A core excipient material are also microencapsulated in dissolved or dispersed liquid phase to obtain appropriate size microparticles. The mixture is then heated if necessary, to evaporate the solvent. Once all the solvent gets evaporated, the mixture temperature is reduced to ambient temperature (if required) with continuous agitation. Also, the particles can be used in isolated form as powders or coated sub states. The obtained material can be either water soluble or insoluble depending on material property. After complete drying of obtained mixture is in the form of new single entity co-excipient [26,27].

iii. Crystallization

Crystallization is a solid crystals formation process of precipitating naturally or artificially from the solution and rarely deposited directly from a gas. It is a chemical solid-liquid separation technique, in which mass transfer of solute from the liquid to crystalline solid is obtained and it must be supersaturated. It means that solution has to contain more solute dissolved, unless equilibrium i.e. Supersaturation is achieved. It can be achieved by various methods such as, solution cooling, addition of second solvent to reduce solubility of the solute or by chemical reaction. Change in pH is one of the most common method used in industry for crystallization.

iv. Hot Melt Extrusion

The technique involves mixing of co-processed excipients with meltable binder on a water bath, and then cooling agglomerates to solidify the mass which is subsequently pass through sieve for size reduction. It is a solvent free technique and requires a less processing time. The concentration of selected excipient ratio is a critical variables in the process. The process is a formation of small pellets, beads from the molten mass which is an extruded through extruder. Schematic presentation shown below (Figure 3).

v. Granulation /Agglomeration

The granulation is a process of forming or crystallizing into grains. The granules typically have size range between 0.2 to 4.0mm depending on their use. The Agglomeration is synonymous to granulation process involves particle size enlargement technique to alter product properties. The Agglomeration process is widely used to enhance physical properties like flowability, bulk density, wettability, and product appearance. In pharma industry two types of granulation technologies are employed, mainly dry and wet granulation. Wet granulation is a more preferred method for co-processing (Table 1).

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JUNIPER PUBLISHERS- ACADEMIC JOURNAL OF POLYMER SCIENCE

Abstract

Novel phenyl-disubstituted propyl 3-(R-phenyl)-2-cyanoacrylates, RPhCH=C(CN)CO2C3H7 (where R is 2-fluoro-5-methyl, 3-iodo-4-methoxy, 5-iodo-2-methoxy, 3,5-dichloro, 3,4-difluoro, 3,5-difluoro, 2-chloro-4-fluoro, 2-chloro-6-fluoro, 3-chloro-2-fluoro, and 3-chloro-4-fluoro) were prepared using condensation of substituted benzoic aldehydes and propyl ester of cyanoacetic acid. The ethynyl benzene copolymerization of novel cyanoacrylates was conducted in solution with radical initiation at 70 C. Nitrogen analysis, 1H & 13C NMR was used to analyze composition and the structure. Thermal behavior of the copolymers was analyzed by DSC and TGA.

Keywords: Radical copolymerization; Styrene copolymers; Trisubstituted ethylene’s; Cyanoacrylates

Introduction

Ring–functionalized trisubstituted ethylene’s (TSE), esters of 3-phenyl-2-cyanoacrylates, R1PhCH=C(CN) CO2R2 continue to attract attention as compounds with interesting properties and as comonomers for modification of commercial polymers. 3,4-Difluorophenyl substituted methyl 3-phenyl-2-cyanoacrylate was used in synthesis and studies of histamine H2 agonistic activity [1]. Ethyl 3-phenyl-2-cyanoacrylate was used in studies of stereoselective cascade assembling of (1R*,2S*)-1-cyano-5,7-dialkyl-4,6,8-trioxo-2-aryl-5,7-diazaspiro[2.5]octane-1-carboxylates [2] and analgesic activity of 6-fluoroindan-1-carboxylic acid [3]. Alkyl 2-cyanoacrylates are a family of vinyl monomers renowned for their high reactivity, instant adhesive properties, and wide-ranging applications [4].

We have reported synthesis and ethynylbenzene copolymerization of similar ring-substituted methyl [5], ethyl [6], & butyl 3-phenyl-2-cyanoacrylates [7]. With the objective to design novel structures, that could serve as a spring board for further development of novel materials with new properties and applications, we have prepared halogen ring-disubstituted propyl 3-phenyl-2-cyanoacrylate (PPCA), RPhCH=C(CN)CO2C3H7sub>, where R is 2-fluoro-5-methyl, 3-iodo-4-methoxy, 5-iodo-2-methoxy, 3,5-dichloro, 3,4-difluoro, 3,5-difluoro, 2-chloro-4-fluoro, 2-chloro-6-fluoro, 3-chloro-2-fluoro, and 3-chloro-4-fluoro, and copolymerize them with ethynylbenzene. To the best of our knowledge, there have been no reports on either synthesis of these propyl phenyl cyanoacrylates, nor their copolymerization with ethynylbenzene.

Experimental

All benzoic aldehydes, propyl cyanoacetate, piperidine, ethynylbenzene, 1,1’-azobiscyclohexanecarbonitrile, (ABCN), and toluene supplied from Sigma-Aldrich Co., were used as received. The melting points and Tg, were measured with TA Model Q10 DSC. The thermal stability of the copolymers was measured by TGA TA Model Q50 from ambient temperature to 800 ºC at 20 ºC/min. The MW of the copolymers was determined by GPC using an Altech 426 HPLC pump at an elution rate of 1.0mL/min; Phenogel 5μ Linear column at 25 ºC and Viscotek 302 detector. 1H & 13C NMR spectra were obtained on 10–25% (w/v) monomer or polymer solutions in CDCl3sub> at ambient temperature using Avance 300MHz spectrometer. Elemental analyses were performed by Midwest Microlab, LLC (IN).

Results and Discussion

PPCA synthesis

The ring-substituted propyl 3-phenyl-2-cyanoacrylates (PPCA) were synthesized by Knoevenagel condensation [8] of a ring-substituted benzoic aldehyde with propyl cyanoacetate, catalyzed by base, piperidine (1).

Where R is 2-fluoro-5-methyl, 3-iodo-4-methoxy, 5-iodo- 2-methoxy, 3,5-dichloro, 3,4-difluoro, 3,5-difluoro, 2-chloro- 4-fluoro, 2-chloro-6-fluoro, 3-chloro-2-fluoro, & 3-chloro-4- fluoro. The preparation procedure was essentially the same for all the monomers. In a typical synthesis, equimolar amounts of propyl cyanoacetate and an appropriate ring-substituted benzoic aldehyde were mixed in equimolar ratio in a 20mL vial. A few drops of piperidine were added with stirring. The product of the reaction was isolated by filtration and purified by crystallization from 2-propanol. The condensation reaction proceeded smoothly, yielding products, which were purified by conventional techniques.

Copolymerization

The PPCA monomers when mixed with ethynylbenzene, EB at EB/PPCA = 3 (mol) formed copolymers as indicated by white flaky precipitates in high excess of methyl alcohol. The conversion of the EB-PPCA copolymers was maintained 10–20% to decrease compositional drift (Table 1). The PPCA content 8.4- 25.8 mol% in the copolymers indicated relatively high reactivity of the PPCA monomers towards EB radical Figure 1.

The EB-PPCA copolymers were soluble in tetrahydrofuran, ethyl acetate, chloroform and dimethylformamide, and insoluble in methyl alcohol, ethyl and petroleum ethers. GPC analysis the copolymers indicated weight-average molecular masses 10.7- 27.8kD (Table 1). According to elemental analysis, between 18.3 & 42.6 mol% of PPCA monomer is present in the copolymers prepared at EB/PPCA = 3 (mol), which is indicative of relatively high reactivity of the monomers towards EB. Results of DSC and TGA analyses are presented in Table 1.

The FTIR spectra of the monomers were compared with those of copolymers and poly(ethynylbenzene) thus providing evidence that the reaction between the PPCA monomers and EB is a copolymerization. The spectra of the copolymers show overlapping bands in 3200–2820cm-1 region corresponding to C-H stretch vibrations. The bands for the PPCA monomer unit are 2246–2238 (w, CN), 1752–1733 (s, C=O), and 1252–1226cm-1 (m, C-O). Benzene rings of both monomers show ring stretching bands at 1500–1400cm-1 as well as a doublet 824–715cm-1, associated with C-H out of plane deformations. These bands can be readily identified in ethynylbenzene copolymers with TSE monomers containing cyano and carbonyl electron withdrawing groups.

EB-PPCA copolymers microstructure analysis is based on 1H and 13C NMR spectroscopy (DEPT, HETCOR, NOESY and JMODXH) of EB copolymers with 2-phenyl-1,1-dicyanoethene [9] which showed the formation of both head-to-tail and headto- head alternating monomer structures, as well as short EB sequences.

Conclusion

Novel phenyl-disubstituted propyl 2-cyano-3-phenyl-2-propenoates were prepared and copolymerized with ethynylbenzene. The compositions of the copolymers were calculated from nitrogen analysis and the structures were analyzed by IR, H1 & 13C-NMR. The thermal gravimetric analysis indicated that the copolymers decompose in in two steps, first in the 200–500C range with residue (1–3%wt), which then decomposed in the 500–800 ºC range.

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Polyelectrolytes : ACUROFLOC range

Anionic and Cationic Polyelectrolytes are used as flocculants in ETP & STP plants.