Bicentric polymerization can occur in the form of cationic polymerization. In 2000, Czech chemists reported the following polymerization reaction initiated by $SnCl_4$.

<MultiModal>![CC(C)=C produces a polymer under the action of $SnCl_4$](/media/uploads/deec3b16-a392-4f34-878f-6f87dd16d145.jpg)</MultiModal>

When exploring the reaction conditions, the researchers discovered the following phenomena:

(1) The reaction can occur well at $20℃$ under an $Ar$ atmosphere; the reaction cannot occur at the same temperature under an oxygen atmosphere.

(2) If there is a small amount of water in the system, the reaction yield decreases.

There are the following statements:

1. Free radicals are involved in the chain initiation process.

2. In the polymer produced by this reaction, there are no secondary carbons directly bonded to secondary carbons.

3. The reaction produces a linear polymer.

4. Polymerization is carried out at $-20℃$ and $20℃$ respectively for the same reaction time, the yield is higher and the number average molecular weight is lower at $20℃$.

5. The water present in the system does not affect the chain initiation process.

Select the option where all the following statements are correct.
双中心聚合反应可以以阳离子聚合的形式出现。2000年，捷克化学家报道了以下 $SnCl_4$ 引发的聚合反应。

<MultiModal>![CC(C)=C在$SnCl_4$作用下产生聚合物](/media/uploads/deec3b16-a392-4f34-878f-6f87dd16d145.jpg)</MultiModal>

探究反应条件时，研究人员发现了如下现象：

(1)$20℃$下在$Ar$气氛下进行反应，反应可以较好地发生；同样温度下在氧气氛下进行反应反应无法发生。  

(2）如果体系中存在少量水，则反应产率下降。

有以下说法：

1.链引发的过程中有自由基参与

2.该反应产生的聚合物中，不存在直接与二级碳成键的二级碳

3.该反应产生的是线性聚合物

4.分别在$-20℃$和$20℃$下进行聚合，反应相同时间，$20℃$下的产率更高但数均分子量更低

5.体系中存在的水不会对链引发过程产生影响

选择以下说法全部正确的一项
No option with all statements correct
1,2,4
2,5,4
3,4,5
2,3,4
1,4,5
1,2,4,5
2,3,5
1,2,3
4,5
1,3,4
1,3,4,5
无说法全部正确的选项
1,2,4
2,5,4
3,4,5
2,3,4
1,4,5
1,2,4,5
2,3,5
1,2,3
4,5
1,3,4
1,3,4,5
The reaction proceeds well under an argon atmosphere, but not under an oxygen atmosphere. Oxygen is a radical scavenger. Since the polymerization chain growth process is a cationic mechanism, free radicals are involved in the reaction during initiation.

<Checkpoint>[Oxygen is a radical scavenger. The reaction cannot proceed under an oxygen atmosphere, indicating that free radicals are involved. Statement 1 is correct.](1)</Checkpoint>

The presence of a small amount of water reduces the yield, indicating the involvement of positive ions. Combining the above information, the following chain initiation mechanism can be obtained:

<MultiModal>![$SnCl_4$ approaches isobutylene CC(C)=C, forming a complex, followed by single electron transfer between the two. An electron is transferred from the isobutylene double bond to $SnCl_4$, generating an isobutylene radical cation. Subsequently, two molecules of the radical cation react to generate C[C+](CC[C+](C)C)C, which has two carbocation reaction active centers, initiating subsequent dicentric polymerization](/media/uploads/2fd52a8b-362f-4c9c-ae39-9aba0cbcf5da.png)</MultiModal>

The key intermediate in this mechanism is the isobutylene radical cation C[C+](C)[C].

The species initiating polymerization is C[C+](CC[C+](C)C)C. The species initiating polymerization itself has a secondary carbon bonded to a secondary carbon, so it is also present in the resulting polymer.

<Checkpoint>[The species initiating polymerization is C[C+](CC[C+](C)C)C](1)</Checkpoint>

<Checkpoint>[The species initiating polymerization itself has a secondary carbon bonded to a secondary carbon, so it is also present in the resulting polymer. Statement 2 is incorrect.](1)</Checkpoint>

The functionality of isobutylene is 2, which can only produce linear polymers.

<Checkpoint>[Since the functionality of isobutylene is 2, the resulting polymer is linear. Statement 3 is correct.](1)</Checkpoint>

Increasing the temperature increases the reaction rate and also allows the initiation reaction to overcome the reaction energy barrier, increasing the yield. At the same time, increasing the temperature will increase the chain termination rate, leading to a decrease in the number-average molecular weight.

<Checkpoint>[Increasing the temperature increases the reaction rate and also allows the initiation reaction to overcome the reaction energy barrier, increasing the yield.](1)</Checkpoint>

<Checkpoint>[Increasing the temperature will increase the chain termination rate, leading to a decrease in the number-average molecular weight. Statement 3 is correct.](1)</Checkpoint>

Water in the system will react with $SnCl_4$ and also quench the carbocations produced by the initiation reaction, which will affect the initiation reaction.

<Checkpoint>[Water reacts with $SnCl_4$ while quenching carbocations, which affects the initiation reaction. Statement 4 is incorrect.](1)</Checkpoint>

Statements 1, 3, and 4 are correct, so option K is correct.
该反应在氩气气氛下反应良好，但在氧气气氛下无法反应，氧气是自由基清除剂，由于聚合链增长过程是阳离子机理，则在引发时有自由基参与反应。

<Checkpoint>[氧气是自由基清除剂，氧气气氛下无法反应，说明有自由基参与，说法1正确](1)</Checkpoint>

存在少量水时会降低产率，说明有正离子参与，结合以上信息，可以得到以下链引发的机理：

<MultiModal>![$SnCl_4$与异丁烯CC(C)=C接近，形成络合物，随后在二者之间发生单电子的转移，异丁烯双键向$SnCl_4$转移一个电子，产生异丁烯自由基正离子，随后两分子自由基正离子发生反应，生成C[C+](CC[C+](C)C)C，具有两个碳正离子反应活性中心，引发后续的双中心聚合](/media/uploads/2fd52a8b-362f-4c9c-ae39-9aba0cbcf5da.png)</MultiModal>

该机理中存在异丁烯自由基正离子C[C+](C)[C]关键中间体。

引发聚合的物种为C[C+](CC[C+](C)C)C，引发聚合的物种自身具有与二级碳成键的二级碳，因此反应产生的聚合物中也存在。

<Checkpoint>[引发聚合的物种为C[C+](CC[C+](C)C)C](1)</Checkpoint>

<Checkpoint>[引发聚合的物种自身具有与二级碳成键的二级碳，因此反应产生的聚合物中也存在，说法2错误](1)</Checkpoint>

异丁烯官能度为2，只能产生线性聚合物。

<Checkpoint>[由于异丁烯官能度为2，因此产生的聚合物为线性，说法3正确](1)</Checkpoint>

温度升高，反应速率增加，同时使得引发反应可以越过反应能垒，产率提高。同时升高温度会使得链终止速率增加导致数均分子量降低。

<Checkpoint>[温度升高，反应速率增加，同时使得引发反应可以越过反应能垒，产率提高。](1)</Checkpoint>

<Checkpoint>[升高温度会使得链终止速率增加导致数均分子量降低，说法3正确](1)</Checkpoint>

体系中的水会与$SnCl_4$反应，同时也会淬灭引发反应产生的碳正离子，会对引发反应产生影响。

<Checkpoint>[水会与$SnCl_4$反应的同时淬灭碳正离子，会对引发反应产生影响，说法4错误](1)</Checkpoint>

说法1，3，4正确，故选项K正确。