Determination of Interaction Parameter χ ofthe 1,2,3-Triazole

Crosslinked Polymer

Dong-Hoon Lee, Sookyeong Lee*, Kyoung Tae Kim**, Hyun-jong Paik*,

Heung BaeJeon**,ByoungSun Min***, and Wonho Kim†

Department of ChemicalEngineering, Pusan National University

*Department of Polymer and Science Engineering, Pusan National University

**Department of Chemistry, Kwangwoon University

***Advanced Propulsion Technology Center, Agency for Defense Development

San 30 Jangjeon-Dong, Gumjung-Gu, Busan 609-735, Korea

**Wolgye-Dong, Nowon-Gu, Seoul 139-701, Korea

***Yuseong, P.O. Box 35, Daejeon 305-600, Korea

______

† Correspondence should be addressed.

E-mail:

ABSTRACT: Thecrosslinking density of polymer can be quantitatively calculated by the Flory-Rehner equation using the swelling experimental data and the lattice constantβ1 of interaction parameter (χ) in this equation should be choosed cautiously. This β1 is the experimental data by rule of thumb, and researchers used little different values respectively. Generally, the average molecular weight between crosslink points Mc in the Flory-Rehner equation and the Mooney-Rivlin equation have the same value, and β1 can be calculated when the Mc in the Flory-Rehner equation is given. Therefore, in this research, firstly we calculated the Mc using the selected β1 (=0.34) and the swelling experimental data of 1,2,3-triazole polymer from theFlory-Rehner equation, secondly the Mcfrom the Mooney-Rivlin equation is calculated by the tensile experimental data, and finally two Mc were compared. As a result, two Mc values were almost same, and it was proved that the β1 (=0.34) was selected properly.

Key words: crosslinking density;Flory-Rehner equation; interaction parameter; Mooney-Rivlin equation; 1,2,3-triazole polymer

I. Introduction

최근우주항공산업의발전과장거리미사일개발이활발하게이루어지면서높은내탄도성능및우수한기계적물성을가지는고에너지로켓추진제의개발이요구된다. 특히저장성이용이하고, 짧은시간동안높은추력을발생시킬수있어고속비행체의가속에적합한복합형고체추진제(composite solid propellant) 의개발이지속적으로연구되고있다. 복합형고체추진제의중요성분인바인더(binder) 는산화제와연료를물리ㆍ화학적으로결합시켜넓은범위의작동온도하에서노출되어있는추진제그레인이만족할만한기계적성질을유지시켜주고추진력발생에필요한연소성물질로도작용한다.1최근에1,2,3-트리아졸네트워크시스템(1,2,3-triazole network system) 으로제작된바인더는수분에민감하지않아비염소계산화제적용에유리하고합성과정중부산물이발생하지않아친환경적인고체추진제바인더기술로서주목을받고있다.2-5 1,2,3-트리아졸결합은아지드(azide) 와에티닐(ethynyl)작용기사이의1,3-이극성고리첨가반응(1,3-dipolar cycloaddition reaction) 에의해만들어지며, Huisgen 이체계적으로연구한이래로다양한반응물과온도,촉매를이용하여여러분야에서연구되었다.6~81,2,3-트리아졸결합으로이루어진고체추진제바인더또한1980년후반부터지금까지많은응용분야에서연구되고있으며, 최근에들어영향력있는특허와연구결과물들이보고되고있다.4,5,7-11

본연구에서는폴리카프로락톤prepolymer로부터제조된1,2,3-트리아졸폴리머의상호계수χ값을구하고자하였다. 인장실험데이터를이용한Mooney-Rivlin으로Mc값을계산후이값을이용하여Flory-Rehner식으로부터상호계수χ값을도출하였다. 도출된χ값과팽윤실험데이터를이용하여β1값을확인하였다.

II. Experimental

본실험에서는폴리카프로락톤을이용하여양말단에아지드기를가지는prepolymer와3 차원망상구조를부여하기위하여말단아지드기가3 개인가교제를합성하였고양말단에에티닐기를가지는경화제를합성하였다. 그후이들을용매와반응촉매없이혼합및가열하여Figure 2와같이1,2,3-트리아졸네트워크를형성하였다.

Prepolymer를합성하기위하여양말단에수산기를가진폴리카프로락톤0260 (3000g/mol) 을바탕으로메틸렌클로라이드하에서메틸술포닐클로라이드(MsCl) 와피리딘을각4 당량을사용하여158 시간동안반응시키고, 탄산수소나트륨(포화), 1M 염산, 증류수로세척한후, 용매를감압증류로제거하여메실화시켰다. 이반응물을아지드화나트륨(NaN3) 10 당량, 디메틸포름아마이드(DMF) 하에서48 시간동안100℃로가열하고, 증류수와메틸렌클로라이드를첨가하여유기용매층으로추출하고감압증류로용매를제거하여양말단을Figure 3 과같이아지드화하였다(수율58%). 가교제는수산기가3개인폴리카프로락톤0310 (900g/mol) 을출발물질로사용하여메틸술포닐클로라이드와피리딘을각5 당량, 아지드화나트륨(NaN3)을15 당량사용하여prepolymer를얻은것과동일한방법으로Figure 3 과같이말단을아지드화시켜사용하였다(수율67%). 경화제의첫번째로에탄디올을프로피올산4 당량과벤젠하에서p-톨루엔술폰산을촉매로하여48 시간동안환류를진행할때, 딘-스탁트랩(Dean-Stark trap) 을사용하여물을제거하였다. 반응이끝난후감압증류로벤젠을제거한다음, 실리카칼럼을통하여Figure 4와같이단분자형태의생성물을얻었다(경화제A, 수율56%). 두번째경화제로올리고머형태의폴리카프로락톤디올(530g/mol) (Aldrich) 에프로피올산을3 당량사용하여앞의경화제와동일한방법으로제조하였다(경화제B, 수율37%). 생성물의구조분석은핵자기공명기(1H NMR, 13C NMR; JNM-AL400 spectrometer, JEOL Ltd., Japan) 와감쇠전반사퓨리에변환적외선분광기(Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy; ATR -FTIR, Nicolet 6700, Thermo Scientific, USA) 를사용하였다.

III. Results and discussion

1,2,3-트리아졸폴리머의결합생성과정을확인하기위하여ATR-FTIR 분석을실시하였으며,아지드화된폴리카프로락톤0260 prepolymer의분석결과를Figure 5(a) 에나타내었고prepolymer와가교제,경화제A 를혼합한지30분후의피크거동을Figure 5(b)에나타내었다. 그리고7일간최종적으로경화를마친후의피크거동을Figure 5(c) 에나타내었다. 아지드화되어서수산기(3230 ~ 3550 cm-1) 피크가사라져있는폴리카프로락톤0260 prepolymer에가교제와에티닐경화제가투입되어혼합한지30분후, 에티닐기(2100 ~ 2260 cm-1, 3170 ~ 3340 cm-1) 의피크가아지드기(2030 ~ 2195 cm-1)피크와중복이되면서나타나는것을알수있었으며, 7일동안경화가진행되면서1,2,3-트리아졸결합이형성되어에티닐기와아지드기의피크가함께사라지는것을관찰할수있었다.이는올리고머형태의경화제B를사용하여도같은거동을나타내었다.

경화제의형태에따른1,2,3-트리아졸폴리머의기계적물성을평가하여그결과를Figure 6와Table 2에나타내었다.경화제A를사용한반응물이경화제B를사용한것보다높은인장강도와모듈러스(100%, 300%)를나타내었으며, 낮은파단신율을나타내었다.단분자형태의경화제A에비해분자량이큰올리고머형태의경화제B가사용된반응물은말단에티닐기가폴리머내에서차지하는비율(index)이낮아최종생성물의가교밀도가낮아진결과로판단된다.

다양한유기용매조건에서1,2,3-트리아졸폴리머의팽윤정도를평가한결과를Figure7에나타내었다. 그결과, 가교폴리머네트워크에서나타나는가우시안형태의그래프를확인할수있었으며, 최대팽윤이일어난지점의용해도상수를폴리머의용해도상수로결정한후가교밀도를계산하여그결과를Table 3에나타내었다.가교밀도가높은경화제A를사용한반응물이경화제B를사용한것보다팽윤도가낮은점에서기계적물성의결과와일치하는것을확인할수있었다.

1,2,3-트리아졸폴리머를이용하여두 가지 계산 방법으로 얻어진 Mc값을 비교해 보고 Mooney-Rivlin 식에서 얻어진 Mc 값을 이용하여 Flory-Rehner 식에 대입 후 얻어진 상호계수χ값과β1값의계산결과를Table 4에나타내었다. 본연구결과두종류의1,2,3-트리아졸폴리머의상호계수χ값이각각0.3609와0.3986 이였으며β1값은일반적으로사용하는0.34에매우근접하였다. 실제로β1을0.0으로하여Flory-Rehner 식으로 계산한 Mc와 Mooney-Rivlin 식의 결과와 비교하였을 때 상당한 차이가 발생하는 점을 알 수 있으며,1,2,3-트리아졸폴리머의 가교밀도를 계산할 때에는 β1을0.34 로적용하여계산하는것이비교적적절한것으로확인되었다.

IV. Conclusions

본연구에서는양말단에아지드기를가지는prepolymer와아지드기가3개인가교제, 그리고양말단에에티닐기를가지는친쌍극자체(dipolarophile) 경화제2 종을합성하여1,2,3-트리아졸네트워크폴리머를제조하였다.기계적물성분석결과,사용된경화제의분자량이작을수록높은가교밀도의형성으로폴리머의인장강도와모듈러스가높아지며파단신율은감소하는결과를나타내었다. 이는팽윤특성에서도일치하는경향을나타내는것을알수있었으며, 다양한유기용매에서실시한팽윤실험을통하여Flory-Rehner식으로Mc를계산할수있었다. 이를Mooney-Rivlin식으로계산된Mc값과비교한결과,두개의Mc값이거의유사하여선정한β1 (=0.34) 값이비교적적절함을증명할수있었으며, 폴리카프로락톤으로제조된두종류의1,2,3-트리아졸폴리머의상호계수χ값이각각0.3609와0.3986임을알수있었다.각 연구 분야별로 Flory-Rehner 식을 사용할 때에는 β1을바로0.34로적용하기전에폴리머의 특성에 따라 미 충전 시스템으로 적절한 β1 값을 확인해 본 후 적용하는 것이 가교밀도 연구에 큰 의미가 있을 것으로 판단된다.

Acknowledgements

이조사연구는국방과학연구소(Grant No; ADD-11-01-07-19)의연구지원으로수행되었기에감사드립니다.

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List of Tables

Table 1. Sample Information

Table 2. Analysis of Mechanical Properties of 1,2,3-Triazole CrosslinkedPolymers

List of Figures

Figure 1.The determination of 2C1 by plotting vs .

Figure 2.The formation of 1,2,3-triazole crosslinked network polymer.

Figure 3.The azidation of prepolymer and crosslinker.

Table 2. Analysis of Mechanical Properties of 1,2,3-Triazole CrosslinkedPolymers

Codes / Elongation at break (%) / Tensile strength (bar) / 100% Modulus (bar) / 300% Modulus (bar)
PA / 605.9 / 13.51 / 2.75 / 5.91
PB / 793.5 / 9.36 / 1.63 / 3.08

Figure2. The formation of 1,2,3-triazole crosslinked network polymer.

Figure3. The azidation of prepolymer and crosslinker.

1