Synthesis and characterization of polyamides containing pendant pentadecyl chains

A new aromatic diacid monomer viz., 4-(4′-carboxyphenoxy)-2-pentadecylbenzoic acid was synthesized starting from cardanol and was characterized by FTIR, ¹H- and ¹³C NMR spectroscopy. A series of new aromatic polyamides containing ether linkages and pendant pentadecyl chains was prepared by phosphorylation polycondensation of 4-(4′-carboxyphenoxy)-2-pentadecylbenzoic acid with five commercially available aromatic diamines viz., 1,4-phenylenediamine, 4,4′-oxydianiline, 4,4′-methylenedianiline, 1,3-phenylenediamine, and 4,4′-(hexafluoroisopropylidene)dianiline. Inherent viscosities of the polyamides were in the range 0.45-0.66 dL/g in N,N-dimethylacetamide at 30 ± 0.1 °C. The introduction of ether linkages and pendant pentadecyl chains into polyamides led to an enhanced solubility in N,N-dimethylacetamide and 1-methyl-2-pyrrolidinone at room temperature or upon heating. The polyamides could be solution-cast into tough, flexible and transparent films from their N,N-dimethylacetamide solution. Wide angle X-ray diffraction patterns exhibited broad halo indicating that the polymers were essentially amorphous in nature. X-Ray diffractograms also displayed a diffuse to sharp reflection in the small-angle region (2θ = ∼2-5°) for the polyamides characteristics of formation of loosely to well-developed layered structure arising from packing of flexible pentadecyl chains. The glass transition temperature observed for the polyamides was in range 139-189 °C. The temperature at 10% weight loss (T₁₀), determined by TGA in nitrogen atmosphere, of the polyamides was in the range 425-453 °C indicating their good thermal stability.     

Regularly alternating poly(amideimide)s containing pendent pentadecyl chains: Synthesis and characterization

Two new aromatic diamines containing preformed amide linkages, viz., N,N′-(4-pentadecyl-1,3-phenylene)bis(4-aminobenzamide) I and N,N′-(4-pentadecyl-1,3-phenylene)bis(3-aminobenzamide) II, were synthesized by reaction of 4-pentadecylbenzene-1,3-diamine with 4-nitrobenzoylchloride and 3-nitrobenzoylchloride, followed by reduction of the respective dinitro derivatives. A series of new poly(amideimide)s was synthesized by polycondensation of I and II with four commercially available aromatic dianhydrides, viz., pyromellitic dianhydride (PMDA), 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 4,4′-oxydiphthalic anhydride (ODPA), and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA) in N,N-dimethylacetamide (DMAc) employing conventional two step method via poly(amic acid) intermediate followed by thermal imidization. Reference poly(amideimide)s were synthesized by polycondensation of N,N′-(1,3-phenylene)bis(4-aminobenzamide) and N,N′-(1,3-phenylene)bis(3-aminobenzamide) with the same aromatic dianhydrides. Inherent viscosities of poly(amideimide)s containing pendent pentadecyl chains were in the range 0.37-1.23 dL/g in N,N-dimethylacetamide at 30 ± 0.1 °C indicating the formation of medium to high molecular weight polymers. The poly(amideimide)s containing pendent pentadecyl chains were found to be soluble in N,N-dimethylacetamide, N,N-dimethylformamide, 1-methyl-2-pyrrolidinone and pyridine and could be cast into transparent, flexible and tough films from their N,N-dimethylacetamide solution. Wide angle X-ray diffraction patterns exhibited broad halo indicating that the polymers were essentially amorphous in nature. X-ray diffractograms also displayed sharp reflection in the small angle region (2θ ≈ 3°) for poly(amideimide)s containing pentadecyl chains indicating the formation of layered structure arising from packing of flexible pentadecyl chains. The glass transition temperatures observed for reference poly(amideimide)s were in the range 331-275 °C and those for poly(amideimide)s containing pendent pentadecyl chains were in the range 185-286 °C indicating a large drop in T_g owing to the “internal plasticization” effect of pentadecyl chains. The temperature at 10% weight loss (T₁₀), determined by TGA in nitrogen atmosphere, were in the range 460-480 °C indicating their good thermal stability.     

Synthesis and characterization of poly(amideimide)s containing pendent flexible alkoxy chains

A series of aromatic diacylhydrazides containing pendent flexible alkoxy chains, viz., 5-butyloxyisophthalicacid dihydrazide, 5-octyloxyisophthalicacid dihydrazide, 5-dodecyloxyisophthalicacid dihydrazide and 5-hexadecyloxyisophthalicacid dihydrazide were synthesized by the hydrazinolysis reaction of the corresponding aromatic esters with hydrazine hydrate. Diacylhydrazides were each polycondensed with aromatic dianhydrides, viz., 4,4′-oxydiphthalic anhydride (ODPA), 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and pyromellitic dianhydride (PMDA) to obtain new poly(amideimide)s. Poly(amideimide)s had inherent viscosity in the range 0.55-0.88 dL/g in N,N-dimethylacetamide (DMAc) at 30 ± 0.1 °C. Poly(amideimide)s were found to be soluble in DMAc, N,N-dimethylformamide (DMF), 1-methyl-2-pyrrolidinone (NMP) and pyridine and could be cast into tough, flexible and transparent films from a solution in DMAc. X-ray diffractograms revealed that poly(amideimide)s with longer alkoxy chains had layered structures. Glass transition temperature of poly(amideimide)s containing pendent flexible alkoxy chains were in the range 215-245 °C. Temperature at 10% weight loss was in the range 380-410 °C in nitrogen atmosphere indicating good thermal stability of poly(amideimide)s.     

Synthesis and characterization of aromatic polyazomethines bearing pendant pentadecyl chains

Aromatic diamine monomer viz., 4-(4′-aminophenoxy)-2-pentadecylbenzenamine containing pendant pentadecyl chain was synthesized starting from cashew nut shell liquid - a renewable resource material and was characterized by FTIR, ¹H and ¹³C NMR spectroscopy. A series of new (co) polyazomethines containing pendant pentadecyl chains and flexibilizing ether linkages was synthesized by polycondensation of 4-(4′-aminophenoxy)-2-pentadecyl benzenamine with commercially available aromatic dialdehydes viz., terephthaldehyde (TPA), isophthaldehyde (IPA) and varying mixture of TPA and IPA. Inherent viscosities and number average molecular weights of (co) polyazomethines were in the range 0.50-0.70 dL/g and 10,490-40-800 (GPC, polystyrene standard), respectively indicating formation of medium to reasonably high molecular weight polymers. (Co) polyazomethines containing pendant pentadecyl chains were found to be soluble in common organic solvents such as chloroform, dichloromethane, tetrahydrofuran, pyridine, m-cresol and could be cast into transparent and stretchable films from their solution in chloroform. (Co) polyazomethines were essentially amorphous in nature and the formation of loosely-developed layered structure was observed arising from the packing of pendant pentadecyl chains. Polyazomethines exhibited glass transition temperatures (T_g) in the range 21-48 °C. The observed depression of glass transition temperature could be ascribed to the “internal plasticization” effect of pentadecyl chains. The temperature at 10% wt loss (T₁₀), determined from TGA in nitrogen atmosphere of polyazomethines were in the range 434-441 °C indicating their good thermal stability.     

Synthesis and characterization of new polyimides containing pendent pentadecyl chains

A new unsymmetrical aromatic diamine, viz., 4-pentadecylbenzene-1,3-diamine was synthesized through a series of reaction steps starting from 3-pentadecylphenol. 4-Pentadecylbenzene-1,3-diamine was employed to synthesize a series of new polyimides by one-step polycondensation in m-cresol with four commercially available aromatic dianhydrides, viz., 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 4,4′-oxydiphthalic anhydride (ODPA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA). Inherent viscosities of resulting polyimides were in the range 0.33-0.67 dL/g and number average molecular weights were in the range 14,700-52,200 (GPC, polystyrene standard). Polyimides containing pendent pentadecyl chains were soluble in organic solvents such as chloroform, m-cresol, N,N-dimethylacetamide (DMAc), 1-methyl-2-pyrrolidinone (NMP), pyridine and nitrobenzene. Strong and flexible films of polyimides could be cast from their chloroform solutions. Polyimides exhibited glass transition temperature in the range 158-206 °C. The temperature at 10% wt. loss (T₁₀), determined by TGA in nitrogen atmosphere, of polyimides was in the range 470-480 °C indicating good thermal stability.     

Synthesis and characterization of new cardo poly(bisbenzothiazole-urea)s containing bulky pendant groups

A series of novel rigid poly(bisbenzothiazole-urea)s (PBTUs III) containing bulky pendant groups were synthesized from 2,2-diaminodibenzothiazoles and aromatic diisocyanates conveniently in the mild condition. The inherent viscosity, solubility, thermal stability, morphology, mechanical and photophysical properties of them were investigated and compared in detail. The inherent viscosities were in the range of 0.58-0.73 dL/g. All of the polymers exhibited excellent solubility in various polar organic solvents. They also showed good thermal stability and mechanical properties. The decomposition temperatures at 10% weight loss were in the range of 368-431 °C in nitrogen. All the PBTUs III were amorphous. Tensile strength of PBTUs III showed the range from 85 to 98 MPa. Compared with poly(benzothiazole)s, all the PBTUs III had the larger optical bandgap and lower photoluminescence quantum yields.     

Synthesis and characterization of new AB-type poly(etherimide)s containing bisphenol moieties

A series of new AB-type poly(etherimide)s having bisphenol-type moiety was prepared by the one-pot polyimidization using triphenylphosphite(TPP) in N-methyl-2-pyrrolidone(NMP)/pyridine solution at 150°C. Complete cyclodehydration was observed in the polymerizations as well as in model reactions. Polymers were obtained with inherent viscosities in the 0.27–0.49 dL/g range. The M_n and M_w/M_n of poly[4-(1,4-phenyleneoxy-1,4-phenylenehexafluoro-isopropylidene-1,4-phenylene)oxyphthalimide] (4d) with η_inh = 0.49 dL/g were 73,400 g/mol and 1.5, respectively. Most polymers could readily be dissolved in common organic solvents such as DMAc, NMP, and m-cresol. The polymer 4d was soluble even in chloroform. These polymers had glass transition temperatures between 205 and 235°C, and 5% weight loss temperatures in the range of 511–532°C in nitrogen. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3530–3536, 1999     

Sulfide and sulfoxide based poly(ether-amide)s: Synthesis and characterization

Two new diacid monomers, 2,2′-sulfide bis(4-methyl phenoxy acetic acid) and 2,2′-sulfoxide bis(4-methyl phenoxy acetic acid) were successfully synthesized by refluxing the 2,2′-sulfide bis(4-methyl phenol) and 2,2′-sulfoxide bis(4-methyl phenol) with chloroacetonitrile in the presence of potassium carbonate, and subsequent basic reduction. Two novel series of poly(sulfide-ether-amide)s and poly(sulfoxide-ether-amide)s with aliphatic units in the main chain were prepared from diacids with various diamines.The polyamides were obtained in quantitative yields and their inherent viscosities were in the range of 0.43-0.89 dl g⁻¹ at a concentration of 0.5 g dl⁻¹ in N,N-dimethylacetamide (DMAc) solvent at 25 °C. They showed good thermal stability. The temperature for 10% weight loss in argon atmosphere was in the range of 350-415 °C. The polymers showed glass transition temperatures between 228 and 261 °C. Almost all of the polyamides were readily soluble in a variety of polar solvents such as N-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO).     

Synthesis and flammability of copoly(isophthalamide)s. II. With pendant phosphorus groups

A series of copoly(isophthalamide)s containing pendant phosphorus, dialkoxyphosphinylphenylene, diphenylphosphinylphenylene, and diphenylphosphinylamino groups were prepared. The introduction of phosphorus groups was performed to a degree of ca. 5–17 mol %. From the limiting oxygen index (LOI) measurements, it was found that the LOI of P-substituted polyamides increased by ca. 14–40%. From TG and DTG analysis the maximum rate and the percentage of mass loss of the decomposition stages were evaluated. From these measurements the mode of action of phosphorus groups in the solid or gas phase was assessed. In the solid phase, due to crosslinking reactions, a reduction of the maximum rate and the percentage of mass loss in the decomposition stage of main chain amide bonds was observed. In this case the increase of the char yield at 700°C of the P-substituted polyamides was in the range of 21–36%. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterization of new poly(arylene ether)s containing heterocyclic units. II.

A series of new poly(arylene ether)s, containing naphthalene, pyridine, and quinoline units have been prepared by solution condensation polymerization. The synthesis involves nucleophilic displacement of aromatic dihalides with aromatic potassium bisphenates in an anhydrous dipolar aprotic solvent at elevated temperatures. The polymers, having inherent viscosity from 0.24 to 1.32 dL/g, were obtained in quantitative yield, have excellent thermal stability as shown by 10% weight loss temperatures in nitrogen and air (above 450 and 430°C, respectively) and high glass transition temperatures (in the range of 150–220°C). The introduction of quinoline moieties in the polymer backbone positively influences the thermal properties, such as high T_g/T_m ratios. © 1995 John Wiley & Sons, Inc.     

Poly(ethylene terephthalate) copolymers containing nitroterephthalic units. I. Synthesis and characterization

The synthesis, microstructure, and thermal behavior of a series of poly(ethylene terephthalate) (PET) copolymers containing nitroterephthalic units are described. These novel copolyesters were synthesized by transesterification followed by melt copolycondensation of dimethyl terephthalate and dimethyl nitroterephthalate mixtures with ethylene glycol. The molar ratio of the two comonomers in the feed varied from 95/5 to 25/75. Furthermore, PET and poly(ethylene nitroterephthalate) homopolymers were synthesized with the same method and comparatively studied. Copolyester compositions were practically the same as in the feed, and weight‐average molecular weights ranged from 10,000 to 60,000. The two monomeric units were randomly distributed along the polymer chain, and the experimentally determined average sequence lengths were in accordance with ideal copolycondensation statistics. Melting temperatures and enthalpies of the copolyesters decreased with increasing content in nitroterephthalic units, and they all showed a single glass‐transition temperature superior to that of PET. They appeared to be stable up to 300 °C, and thermal degradation occurred in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3761–3770, 2000     

Synthesis and characterization of poly(aryl ether)s containing the pyrimidine moiety

A series of new poly(aryl ether)s containing the pyrimidine moiety were prepared by a nucleophilic aromatic substitution polymerization reaction in an aprotic solvent (DMAc) in the presence of excess potassium carbonate. These polymers are high molecular weight, amorphous, and soluble in common solvents at room temperature. The polymers are easily cast from solution into flexible, colorless, and transparent films. They showed high glass transition temperatures ranging from 198 to 304°C by DSC analysis. The 5% weight losses by thermogravimetric analysis ranged from 478 to 580°C, indicating that these polymers are very thermostable in nitrogen and air. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1107–1110, 1998     

Synthesis and characterization of new copolymers of thiophene and vinylene: Poly(thienylenevinylene)s and poly(terthienylenevinylene)s with thioether side chains

Poly[3,4-bis(3-methylbutylthio)thienylenevinylene], poly[3,4-bis-(S)-(2-methylbutylthio)thienylenevinylene], poly[3′,4′-bis(3-methylbutylthio)-2,2′:5′,2″-terthienylene-5,5″-vinylene], and poly{3′,4′-bis-(S)-[2-methylbutylthio]-2,2′:5′,2″-terthienylene-5,5″-vinylene} have been synthesized. The synthesis starts from the thiophene monomers and trimers, which are formylated to give the corresponding dialdehydes. The dialdehydes are reductively polymerized using a McMurry coupling. The polymers are characterized by GPC, optical spectroscopy (FT-IR, UV-vis, circular dichroism spectroscopy and photoluminescence) and by proton and carbon NMR spectroscopy. The polymers are soluble in common organic solvents, such as THF, chloroform, toluene, benzene and 1,2-dichlorobenzene. The solvatochromism and thermochromism of the polymers in solution are investigated, while the optical activity of the polymers is used to investigate the supramolecular aggregation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4629–4639, 1999     

新型聚酰胺酰亚胺的合成及其热稳定性

L-丙氨酸与均苯四甲酸二酐经缩合反应制得手性酰亚胺(1);1与二苯基甲烷二异氰酸酯聚合制得新型的以L-丙氨酸为手性源的聚酰胺酰亚胺(2),其结构经1H NMR和FT-IR表征.用DSC和TGA研究了2的结晶性能和热稳定性,同时对2的溶解性能进行了探讨.结果表明,2的Tm为357.6℃,失重5％的分解温度为215℃;2在常温下溶于DMF,DMAc,DMSO和NMP.     

Synthesis and characterization of copoly(arylene sulfide)s

Copolymerizations of p-dichlorobenzene (DCB)/4-bromophenyl ether (BPE), DCB/4,4′-dibromobiphenyl (DBB), and DBB/BPE pairs with sodium sulfide under high temperature (270–290°C) utilizing N-methyl-2-pyrrolidinone (NMP) as solvent were carried out to give C(DCB/BPE), C(DCB/DBB), and C(DBB/BPE) copolymers, respectively. The reactivity of dihaloaromatic monomers toward thiolate anion in the polycondensation reaction followed the order DBB > DCB > BPE. The reactivity gap between DBB and DCB toward thiolate anion seemed to be smaller than that between BPE and DCB, resulting in both high yield and high molecular weight in the C(DCB/DBB) copolymers compared to C(DCB/BPE) copolymers. The copolymerization of DBB/BPE pair with sodium sulfide, which has larger reactivity gap than the DCB/DBB or DCB/BPE pair, gave mixtures of PBS and PPSE homopolymers especially in the range of 50–80 mol % BPE in the feed. The C(DCB/DBB) and C(DCB/BPE) copolymers, however, exhibited random copolymer character in all comonomer ratios in the feed as evidenced by copolymer composition and DSC data. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2311–2317, 1999     

Synthesis of poly(silyl ether)s containing pendant chloromethyl groups by the polyaddition of bis(oxetane)s with dichlorosilanes

The polyaddition of bis(3‐ethyl‐3‐oxetanylmethyl) terephthalate (BEOT) with dichlorodiphenylsilane (CPS) using tetrabutylammonium bromide (TBAB) as a catalyst proceeded under mild reaction conditions to afford a polymer containing silicon atoms in the polymer main chain. A poly(silyl ether) (P‐1) with a high molecular weight (M_n = 53,200) was obtained by the reaction of BEOT with CPS in the presence of 5 mol % of TBAB in toluene at 0 °C for 1 h and then at 50 °C for 24 h. The structure of the resulting polymer was confirmed by IR and ¹H NMR spectra. Furthermore, it was proved that the polyaddition of certain bis(oxetane)s with dichlorosilanes proceeds smoothly to give corresponding poly(silyl ether)s with TBAB as the catalyst. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2254–2259, 2000     

Poly(diarylsilmethylene)s,I. Synthesis and characterization

Poly(diarylsilmethylene)s with phenyl or tolyl substituents on Si atoms were synthesized by ring-opening polymerization of corresponding 1,1,3,3-tetraaryl-1,3-disilacyclobutanes, and were characterized by means of DSC, x-ray diffraction and melt viscosity measurements. Three preparative routes including catalytic and noncatalytic polymerization methods were examined to see differences in properties of the resulting polymers. The polymers thus obtained were crystalline and soluble in limited solvents such as diphenyl sulfone at tem-peratures above 250°C. Poly(diphenylsilmethylene) exhibited a melting temperature of about 350°C, whereas those of polymers with tolyl groups were observed in a temperature range between 310 and 330°C. The melt viscosity of the poly(diarylsilmethylene)s was measured to obtain insight into the molecular weights of the polymers, and the results indicated that the molecular weights are modifiable by varying the monomer-to-catalyst ratio when solution polymerization is employed. The DSC and x-ray studies were also carried out with focusing on the melting and crystallization behavior of these polymers. © 1995 John Wiley & Sons, Inc.     

Poly(phenylsilsesquioxane)s: Structural and morphological characterization

Poly(phenylsilsesquioxane) (PPSQ) polymers that were obtained from different synthetic routes were comparatively studied. The polymers were characterized by infrared and solid‐state ²⁹Si NMR spectroscopies. According to the results of X‐ray diffraction and thermogravimetric analyses, the materials richest in silanol showed a less organized network and lower weight loss temperature. The morphology of the products was influenced by the preparation conditions. PPSQ, with a morphology rich in spherical particles, was achieved with an n‐hexadecyltrimethylammonium bromide template in the reaction medium, whereas the morphology of this polymer obtained in the absence of the template was featureless. Small‐angle X‐ray scattering analyses revealed that the PPSQ samples showed a predominance of surface‐fractal behavior. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1580–1589, 2000     

Poly(ethylene terephthalate) copolymers containing 5‐nitroisophthalic units. I. Synthesis and characterization

Poly(ethylene terephthalate‐co‐5‐nitroisophthalate) copolymers, abbreviated as PETNI, were synthesized via a two‐step melt copolycondensation of bis(2‐hydroxyethyl) terephthalate and bis(2‐hydroxyethyl) 5‐nitroisophthalate mixtures with molar ratios of these two comonomers varying from 95/5 to 50/50. Polymerization reactions were carried out at temperatures between 200 and 270 °C in the presence of tetrabutyl titanate as a catalyst. The copolyesters were characterized by solution viscosity, GPC, FTIR, and NMR spectroscopy. They were found to be random copolymers and to have a comonomer composition in accordance with that used in the corresponding feed. The copolyesters became less crystalline and showed a steady decay in the melting temperature as the content in 5‐nitroisophthalic units increased. They all showed glass‐transition temperatures superior to that of PET with the maximum value at 85 °C being observed for the 50/50 composition. PETNI copolyesters appeared stable up to 300 °C and thermal degradation was found to occur in two well‐differentiated steps. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1934–1942, 2000     

Synthesis and characterization of calcium containing poly(urethane-ether)s

Calcium containing poly(urethane-ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate or toluylene 2,4-diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and polyethylene glycol (PEG₂₀₀ or PEG₄₀₀). A series of calcium containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:PEG₂₀₀ or PEG₄₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4 and 1:3:4 to study the effect of calcium content on the properties of the copolymer. The structure of the polymers were confirmed by IR, ¹H-NMR, ¹³C-NMR, and solid state ¹³C-CP-MAS NMR. The polymers were soluble in dimethyl sulfoxide and dimethyl formamide. The initial decomposition temperature of the polymers decreases with increase in calcium content. The T_g value of PUEs increases with increase in calcium content and decreases with increase in soft segment content and length. A single T_g value is observed for the calcium containing PUEs based on PEG₂₀₀ shows the presence of homogeneous phase. However, two T_g values for the PUEs based on PEG₄₀₀ for various composition of Ca(HBP)₂, PEG₄₀₀ and diisocyanate (HMDI or TDI) shows the presence of heterogeneous phase. The viscosity of the calcium containing PUEs increases with increase in the soft segment content as well as its length and decreases with increase in calcium content. X-ray diffraction patterns of the polymers show that the HMDI based polymers are partially crystalline and TDI based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium containing PUEs based on HMDI shows that at any given temperature modulus (g^′ and g^″) increases with increase in the ionic content in the polymers.