3. Ring opening polymerization (ROP)
3-1. 개요
1) 선형고분자를 합성하는 방법은 축합중합, 부가중합, 개환중합이다
2) 많은 종류의 heterocyclic 화합물은 개환중합된다.
①
②
③
④
polyethers prepared from cyclic ethers
polyamides from cyclic amides (lactams)
polyesters from cyclic esters (lactones)
polysiloxanes from cyclic siloxanes 등
3. Ring opening polymerization (ROP)
3) 특징
① ROP does not lose small molecules or unsaturation
② ROP shows the characteristics of step-growth and of chain-growth polymerization
i) the molecular weight increases relatively slowly with conversion
ii) the monomer adds to the growing chains in propagation step and propagation rates are
usually described by equations resembling those of chain-growth polymerization
③ ROP is primarily initiated by ionic initiators. Water is used as an initiator for very reactive
cyclic monomer
④ the ionic ROP exhibit most of the characteristics of anionic and cationic polymerization of
vinyl monomers, such as the effects of solvent and counter ion
⑤ ceilng temperatures of ROP are often quite low as compared to vinyl polymerization,
and consequently kinetics may be complicated by the occurrence of polymerization
-depolymerization equilibrium
3. Ring opening polymerization (ROP)
3-2. Cyclic ethers/epoxides
1) 음이온 중합
① ethylene oxide (epoxide)의 initiation and propagation
i) 개시제는 hydroxide, alkoxides, metal oxides 등
ii) 예 : K+(t-BuO)-
② termination
i) epoxide polymerization has the characteristics of living polymerization, that is,
initiation is fast relative to propagation and there is an absence of termination
ii) 정지반응은 양성자성 시약(HO-H, RO-H, RCOO-H, R2N-H)을 첨가해야 일어난다
polyethylene oxide or polyethylene glycol
3. Ring opening polymerization (ROP)
③ kinetics
i) the polymerization rate is given by
𝑅𝑝 = −
𝑑𝑀
= 𝑘𝑝 𝑀− 𝑀 = 𝑘𝑝 𝐶𝐴
𝑑𝑡
0
𝑀
ii) the number averaged degree of polymerization at time t is given by
𝑋𝑛 =
𝑀
− [𝑀
𝐶𝐴 0
0
3. Ring opening polymerization (ROP)
④ propylene oxide의 음이온중합
i) low MW (<5000) polymer is obtained since chain growth is severely restricted by
chain transfer to monomer
ii) chain transfer occurs by α-proton abstraction from the methyl group attached to
the epoxide ring
possible to add monomers
polypropylene oxide or polypropylene glycol
3. Ring opening polymerization (ROP)
3) 양이온 중합
① tetrahydrofuran(THF)의 initiation and propagation
i) 개시제는 protic acid, Lewis acid-cocatalyst 등
ii) 반응성이 약한 THF는 BF3 등과 같은 양이온 개시제에 의해서만 중합이 될 수 있다
- the α-carbon of the oxonium ion is being electron-deficient because of the
adjacent positively charged oxygen, propagation involves a nucleophilic attack of
the oxygen of a monomer molecule on the α-carbon of the oxonium ion
- the product of propagation has a terminal cyclic oxonium ion formed from the
newly added monomer molecule.
3. Ring opening polymerization (ROP)
② tetrahydrofuran(THF)의 termination and chain transfer
i) termination with counter ion
polytetramethylene oxide
ii) chain transfer to polymer
iii) chain transfer to externally added chain transfer agent such as water or ammonia
3. Ring opening polymerization (ROP)
③ 1,3,5-trioxane도 양이온 개시제에 의해서 중합된다.
i) initiator : boron trifluoride etherate (water is required)
ii) initiation and propagation
3. Ring opening polymerization (ROP)
iii) chain transfer and termination ; by combination with either counter ion or an
anion derived from it
iv) end-blocking is performed to prevent depolymerization
if initiator is triethyloxonium tetrafluoroborate, then the initiation gives
3. Ring opening polymerization (ROP)
④ kinetics
i) the rate of the cationic ROP of cyclic ethers :
𝑅𝑝 = 𝑘𝑝 𝑀 + 𝑀
ii) for reversible ROP, the propagation-depropagation equilibrium can be expressed by
𝑅𝑝 = −
𝑑𝑀
𝑑𝑡
= 𝑘𝑝 𝑀+ 𝑀 − 𝑘𝑑𝑝 𝑀+
as the rate of polymerization is zero at equilibrium
𝑘𝑝 𝑀
−
𝑑𝑀
𝑑𝑡
𝑒
= 𝑘𝑑𝑝
where [M]e is the equilibrium monomer concentration
= 𝑘𝑝 𝑀 + ( 𝑀 − 𝑀 𝑒 )
Integration gives
ln(
𝑀 𝑜− 𝑀 𝑒
)
𝑀−𝑀𝑒
= 𝑘𝑝 𝑀 + 𝑡
where [M]o is the initial monomer concentration
3. Ring opening polymerization (ROP)
3-3. Cyclic amides (lactams)
linear polyamide를 생성하는 lactam (cyclic amide)의 개환중합은 공업적으로 중요
1) ε-caprolactam(6-hexanolactam)으로부터 nylon 6 중합
① 강염기(alkali metal, metal amide, alkoxide)에 의한 개시
i) ring opening of the initiated monomer does not occur. since the lactam anion is
stabilized by resonance
3. Ring opening polymerization (ROP)
ii) it attacks the carbonyl atom in a molecule of monomer very slowly, causing
scission of the CO-NH bond to produce a highly reactive terminal-NH- ion
iii) the primary amine anion is highly reactive because it is not stabilized by
conjugation with a carbonyl group
3. Ring opening polymerization (ROP)
② propagation step
i) 1차 아민 음이온은 다른 lactam 분자로부터 신속히 양성자를 추출하여
amino acyl lactam으로 된다.
ii) amino acyl lactam과 lactam anion과 반응한다. 공격받는 lactam 고리가 두 번째
카르보닐기에 의해 활성화되기 때문에 개시반응보다 훨씬 빠르다.
3. Ring opening polymerization (ROP)
iii) 계속하여 단량체가 개환중합되면서 성장한다.
iv) 반응성을 가속하기 위해 acylating agent (acid chloride, anhydride)를 첨가해 주는데,
이것을 활성제(activator)라고 한다.
3. Ring opening polymerization (ROP)
2) 가수분해중합(hrdrolytic polymerization) … 물을 소량 첨가
① the water initiates the reaction by attacking the carbonyl to form the open chain
species, ε-aminocaproic acid
② propagation은 다음 두 가지 경로가 가능하다
i) ring opening polymerization
3. Ring opening polymerization (ROP)
- 이 반응은 소량의 산을 첨가하면 촉진된다
(가수분해된 아미노산에서 프로톤이 방출되면서 반응을 활성화 시킨다)
ii) step polymerization of amino acid
3. Ring opening polymerization (ROP)
3-4. Cyclic esters (lactones)
1) lactone은 음이온중합과 양이온중합을 통하여 polyester를 형성할 수 있다.
① cationic polymerization is not as useful as anionic polymerization for synthesizing
high MW polyesters due to detrimental side reactions such as intramolecular
transesterification and chain transfer to polymer which lower the MW
2) ε-caprolactone(6-hexanolactone)으로부터 aliphatic polyester 중합 : 상업적 중요
① 염기에 의한 음이온중합
3. Ring opening polymerization (ROP)
3) poly(lactic acid) or polylactide
X
i) direct polycondensation of lactic acid … low MW PLA
ii) two step polymerization … limited by equilibrium reaction due to hydrolysis of ester
iii) ROP of lactide … high MW PLA
3. Ring opening polymerization (ROP)
- 연습문제 1 polymerization of 3.45 M of ethylene oxide with 1.36x10-3 M of potassium tertbutoxide in DMSO was done and polymerization rate was determined as
0.99x10-3 mol/L·s what is kp and what is DP at 90% conversion?
𝑘𝑝 =
𝑋𝑛 =
𝑅𝑝
𝐶𝐴 0 𝑀
𝑀
− [𝑀
𝐶𝐴 0
0
3. Ring opening polymerization (ROP)
- 연습문제 2 Cyclic ether와 동일하게 cyclic amine도 개환중합을 거쳐 polyamine으로 만들 수 있다.
1) 개시제로 protic acid HA를 사용하여 중합하는 과정을 화학반응식으로 나타내라
2) aziridinium ion과 성장하고 있는 고분자쇄가 반응하여 branch가 생성되는 과정을
화학반응식으로 기술하라.
3. Ring opening polymerization (ROP)
- 연습문제 3 실험 1. (C2H5) 3)O+BF4-를 개시제로 사용하고 최초 개시제 농도를 0.61 x 10-2 mol/L 로 하여
tetrahydrofuran을 0oC에서 중합하고 측정한 초기중합속도, Rp는 표 1과 같다.
실험 2. [M]0=6.1 mol/L, [I] 0=3.05 x 10-2 mol/L 의 조건에서 중합시키면서 시간 (t)의 함수
로 측정한 monomer conversion (p) 을 표 2에 나타내었다. 중합을 종결시키기
위하여 소량의 물을 첨가하였다
표1
표2
[M]o, mol/L
Rp, mol/L . min
t, min
p
Mn
9.15
0.00930
24
0.085
-
8.00
0.00820
48
0.207
-
7.00
0.00680
84
0.310
4078
6.10
0.00500
162
0.443
-
5.00
0.00350
210
0.490
-
4.06
0.00170
398
0.565
-
3.05
0.00037
1) initiation, propagation, termination에 대한 반응식을 기술하라
3. Ring opening polymerization (ROP)
2) equilibrium monomer concentration을 구하라
x축을 [M]0, y축을 Rp x 103 mol/L min로 하여 plot한 후, Rp = 0 에서의 값이 [M]e 이다
3) propagation rate constant kp at 0oC 를 구하라
①
Monomer conversion, p =
x축을 t, y축을 ln(
②
𝑋𝑛 =
𝑀
0
− [𝑀
𝐼0
𝑀 𝑜− 𝑀
𝑀𝑜
𝑜𝑟
𝑀 = 𝑀 𝑜 (1 − 𝑝)
𝑀 𝑜− 𝑀 𝑒
) 로 하여 plot 하면 기울기가 𝑘𝑝 𝑀+ 이다
𝑀 − 𝑀𝑒
=
𝑀
0
− [𝑀
로부터 𝑀+ 의 계산
+
𝑀
Mn = 46 + 72x = 4078 … x = Xn … 𝑀 = 𝑀 𝑜 (1 − 𝑝) 를 구한 후 𝑀+ 을 계산한다
𝑘𝑝 𝑀+
𝑘𝑝 =
𝑀+
3. Ring opening polymerization (ROP)
- 연습문제 4 ε-caprolactam의 음이온 중합시 lactam anion과 caprolactam간의 반응 속도는 느리지만,
lactam anion과 acyl lactam과의 반응은 빠르게 일어난다. 그 이유를 아래 반응들의 생성물
의 구조를 그린 후, 생성물의 안정성을 통하여 설명하라