방향족 폴리에스테르의 합성에 관한 상이동 촉매의 특성고찰

하동헌, 문정열, 김경훈, 이화수, 박대원, 이진국*

부산대학교 화학공학과, 부산대학교 고분자공학과*

CHARATERIZATION OF PHASE TRANSFER CATALYST ON SYNTHESIS OF AROMATIC POLYESTER

D.H.Ha, J.Y.Moon, K.H.Kim, H.S.Lee, D.W.Park, and J.K.Lee*

Dep. of Chemical Eng., Pusan National University,

Dep. of Polymer Eng., Pusan National University*

INTRODUCTION

Aromatic polyesters having pendant functional group are an important class of functional polymers, because they find a variety of useful application such as composite materials, electric conductive polymers and polymer catalysts. However, research is restricted mostly to synthesis of vinyl-type addition polymers.[1] Recently, attention has been paid to reactive aromatic polyester and these polyesters behave differently from that of vinyl-type addition polyesters.[2]

In this study, aromatic polyesters having pendant carboxyl group were synthesized by the organic/water phase interfacial polycondensation using phase transfer catalyst. Polyester having pendant quaternary ammonium salts group in the side chain also used as phase transfer catalyst. we have investigated the synthesized aromatic polyesters in view of the charateristics of phase transfer catalyst and their thermal property were also studied.

EXPERIMENTAL

The synthesis of aromatic polyester was carried out in an water/organic phase interfacial polycondensation. 0.01mol of isophtaloyl dichloride(IPDC) in 40 ml of organic solvent was added to 0.01mol of 4,4-bis(p-hydroxyphenyl) valeric acid(DPA) in 90ml of 1N aqueous NaOH solution in the present of phase transfer catalyst. The mixture was stirred for 1h at 25℃, polyester precipitated was filterd, washed by 0.01N hydrochloric acid, deionized water and then aceton, and dried for 8h at 70℃ in vaccum. the polymer catalyst was prepared by an organic phase/organic phase interfacial polycondensation of isophtalic dichloride with triethyl-2,3-propanediolammonium chloride. The identification of polyester was performed by React-IR(ASI-2000) and the molecular weight was measured by GPC(WATERS 2040). The thermal properties of the polymer were charaterized with DSC(Dupont 2000) and TGA(Dupont).

RESULTS AND DISCUSSION

The synthesis of aromatic polyester was carried out using various phase transfer catalysts and polymer catalyst. The IR spectrum of polyester shows an absorption band of 2970, 2930, 2870, 1740, 1700, 1580 cm-1 due to  -CH3, -CH2-, -OH, -COO-, -COOH, aromatic C-H,  respectively.[3]

Interfacial polycondensation is a very complex reaction. molecular weight of the resulting polymer is remakably affected by phase transfer catalyst and reaction condition. Quaternary ammonium salts, used most commonly in industrial fields showed a good catalytic activity in the water/organic phase interfacial polycondensation. The higher molecular weight obtained with quaternary ammonium salts catalyst having larger alkyl group as shown in Fig. 1. Bulky quaternary salts, having longer distance between cation and anion are generally known to exhibit higher activity in activating anions. Fig. 2 shows that the molecular weight with different halide anions of the quaternary ammonium salts increases in the order of Cl- < Br- < I-. This is consistent with the nucleophilicity of the halide anions in nonpolar solvent such as dichloromethane.[4]

The catalytic activity of crown ethers, as shown in Fig. 3 and 4, the ones with larger cavity size and have more stable molecular structure showed good catalytic activity. when crown ether has larger cavity size, bonding can be easily occured between crown ether and diphenolic acid which has Na+ ion. so it is easier to transfer diphenolic acid which resolved in water phase to organic phase and makes reaction.

As shown in Fig. 5. The molecular weight of polyester increased with reaction time until 1hour and then decreased. it is due to hydrolysis of esterification. the esterification reaction between diphenolic acid and isophtalic acid occur rapidly until 1hour but exceed reaction time make hydrolysis. consequently, decomposition of polyester is initiated at this point. High molecular weight aromatic polyester can be obtained by polymer catalyst. the polymer catalyst contributes to the increased in molecular weight due to the nucleophilic catalytic action of pendant ammonium group and the phase transfer of the resulting intermediate from the organic phase to the aqueous phase. the intermediate of nucleophilic catalyst resulting from pendant  ammonium group of the polymer catalyst and isophtalic chloride produces a polymer effect, i.e., the nucleophilic attack of the Cl- ion in pendant ammonium group on the carbonyl carbon is promoted by nonpolar solvent which around the intermediate. Fig. 6. shows the effect of different alkyl groups attached on polymer catalyst. the molecular weight is the highest when polymer catalyst having smaller alkyl group. this result indicates that polymer catalyst having larger alkyl group hardly contacts with reactants because of  stereo hinderance.

The study on the thermal properties of polyesters were performed by DSC measurements. Fig. 7. show the Tgs of polyesters prepared with various diols. The Tgs of polyesters decreased in the order of Bisphenol-A > Propyl Chlorohydrin Diphenolate > N-Ethyldiethanolamine > 3-Chloro-1,2-propane diol. The polyester with 3-Chloro-1,2-propanediol showed lower thermal stability than polymer  having higher Tg such as bispenol-A. This fact may be due to flexibility of aliphatic chain.

CONCLUSIONS

Aromatic polyesters having pendant carboxyl group were synthesized by the organic/water phase interfacial polycondensation using phase transfer catalyst. in case of quarternary ammonium salts, the ones with higher alkyl chain length and with more nucleophilic counter anion showed higher catalytic activity.

The catalytic activity of crown ethers, the ones with larger cavity size and have more stable molecular structure showed good catalytic activity.

Polyester having pendant quaternary ammonium salts group in the side chain also used as phase transfer catalyst and it showed better catalytic activity than other phase transfer catalyst.

A novel type of polyesters were synthesized and their thermal stability was in the order of Bisphenol-A > Propyl Chlorohydrin Diphenolate > N-Ethyldie -thanolamine > 3-Chloro-1,2-propanediol.

REFERENCE

[1] C. Wang and S. Nakamura,  J. Polym. Sci., A, Polym. Chem., 32, 1255        (1994).

[2] J. M. Bruce and J. R. Herson, .polymer, 8, 619(1967)

[3]  H. Schnell, Angew. Chem., 68, 633(1956).

[4] C. M. Starks, C. L. Liotta and M. Halpern, "Phase Transfer Catalyst",        Chapman & Hall, New York(1994).

Figure 7. DSC curve of polyester