【作者】 李军；

【导师】 张先宏；

【作者基本信息】 北京化工大学 ， 材料科学与工程， 2024， 硕士

【摘要】 液体异戊二烯橡胶（LIR）是一类低分子量的合成橡胶,因其独特的液体形态和优异的加工性能,在橡胶和聚氨酯等领域具有广泛的应用前景。然而,LIR本身缺乏反应性基团,限制了其在功能化弹性体材料制备及加工中的应用。本文采用可逆加成-断裂链转移（RAFT）聚合技术,设计合成了两类双端功能化“遥爪型”LIR,分别为双端羧基聚异戊二烯（CTPI）和双端羟基聚异戊二烯（HTPI）,并采用后修饰的方法制备了两端端基为巯基-羧基的聚异戊二烯（SCPI）。在后续工作中系统研究了CTPI在异戊橡胶和HTPI在聚氨酯弹性体中的应用,重点探究了LIR分子结构与材料微观形态和宏观性能间的构效关系。首先,合成双端羧基封端的RAFT试剂和双端羟基封端的RAFT试剂,并将其分别用于介导异戊二烯的可控聚合。通过调节单体与RAFT试剂的投料比,制备了一系列分子量分布窄（?<1.60）、端基结构明确的CTPI和HTPI。¹H NMR及FTIR表征结果表明,RAFT试剂能够有效控制产物的分子量和端基结构,所得LIR以1,4-结构单元为主（约90%）,顺反构型比约为1:2。此外,使用正丁胺对RAFT聚合产物进行三硫酯的脱除,通过表征证明成功得到了结构明确的目标产物SCPI。后续主要针对CTPI和HTPI进行了应用探究。在CTPI的应用研究中,将其作为橡胶加工助剂掺入异戊橡胶基体,发现CTPI能够显著提高橡胶的加工性能。这是由于CTPI端基上的极性基团能够增加橡胶与补强填料间的相容性,改善胶料的分散性。进一步向体系中引入Fe³⁺,可与CTPI端羧基通过配位作用形成动态可逆键,在硫化橡胶内部构筑双交联网络结构,从而提升橡胶的拉伸强度。研究发现,当Fe³⁺与CTPI羧基的摩尔比为0.10、CTPI分子量为27000 g/mol时,所得复合材料的综合力学性能最佳,拉伸强度较纯异戊橡胶提高37.86%。针对HTPI的应用,本文以HTPI为软段合成了一系列聚氨酯弹性体。通过调控HTPI分子量（1800～3900 g/mol）、聚氨酯硬段含量（15～25wt%）以及扩链剂与交联剂的比例（BDO:TMP为9:1～3:1）,系统研究了不同变量对聚氨酯微观相分离结构和力学性能的影响。研究发现,HTPI分子量的增大会对材料微观结构造成影响,从而导致材料的玻璃化转变温度以及储能模量降低,同时对材料的力学性能产生一定影响。硬段含量的变化主要影响材料的强度,而扩链剂与交联剂比例的变化主要影响聚氨酯的交联密度和韧性。当软段分子量为2100 g/mol、硬段含量为25 wt%、BDO:TMP比为9:1时,聚氨酯弹性体在保持高强度（拉伸强度11.6 MPa）的同时具有良好的延展性（断裂伸长率约450%）。此外,基于HTPI分子链上的不饱和双键,通过硫化交联对聚氨酯进行化学改性,进一步提高了材料力学强度,尤其是对线性聚氨酯体系。更多还原

【Abstract】 Liquid isoprene rubber（LIR）is a class of low molecular weight synthetic rubber that exhibits a wide range of applications in the rubber and polyurethane industries due to its unique liquid state and excellent processing properties.However,the lack of reactive groups in LIR limits its application in the preparation and processing of functionalized elastomeric materials.In this study,two types of telechelic LIRs with functional end groups,namely carboxyl-terminated polyisoprene（CTPI）and hydroxyl-terminated polyisoprene（HTPI）,were designed and synthesized using reversible addition-fragmentation chain transfer（RAFT）polymerization.Additionally,thiol-carboxyl terminated polyisoprene（SCPI）was prepared through post-modification.The applications of CTPI in isoprene rubber and HTPI in polyurethane elastomers were systematically investigated,focusing on the relationships between the molecular structure of LIR and the microscopic morphology and macroscopic properties of the materials.Firstly,RAFT agents with carboxyl and hydroxyl end groups were synthesized and used to mediate the controlled polymerization of isoprene.By adjusting the feed ratio of monomer to RAFT agents,a series of CTPI and HTPI with narrow molecular weight distributions（?<1.60）and well-defined end group structures were prepared.The results of ¹H NMR and FTIR spectroscopy characterizations demonstrated that the RAFT agents could effectively control the molecular weight and end group structure of the products.The obtained LIRs were mainly composed of 1,4-structural units（about 90%）with a cis/trans ratio of approximately 1:2.Furthermore,the trithiocarbonate group was removed from the RAFT polymerization products using n-butylamine,and the successful synthesis of the target product SCPI with a well-defined structure was confirmed through characterization.The applications of CTPI and HTPI were subsequently explored.For CTPI application,it was incorporated into isoprene rubber as a processing aid and found to significantly improve the processing properties of the rubber.This improvement was attributed to the polar groups on the end groups of CTPI,which increased the compatibility between the rubber and the reinforcing fillers,thereby enhancing the dispersion of the rubber compound.Further introduction of Fe³⁺into the system led to the formation of dynamic reversible bonds with the carboxyl end groups of CTPI through coordination interactions,constructing a dual-crosslinked network structure within the vulcanized rubber and thus improving the mechanical strength of the rubber.It was found that the optimal comprehensive mechanical properties were achieved when the molar ratio of Fe³⁺to CTPI carboxyl groups was 0.10 and the molecular weight of CTPI was 27,000 g/mol,with the tensile strength of the composite material increasing by 37.86%compared to pure isoprene rubber.For the application of HTPI,a series of polyurethane elastomers were synthesized using HTPI as the soft segment.The effects of HTPI molecular weight（1,800-3,900 g/mol）,polyurethane hard segment contents（15-25 wt%）,and the ratio of chain extender to crosslinker（BDO:TMP from 9:1 to 3:1）on the microphase separation structures and mechanical properties of the polyurethanes were systematically investigated.It was found that the increased molecular weight of HTPI influenced the microscopic structure of the material,leading to a decrease in the glass transition temperature and storage modulus,as well as impacting the mechanical properties to some extent.Changes in the hard segment content mainly affected the strength of the material,while variations in the ratio of chain extender to crosslinker primarily influenced the crosslink density and toughness of the polyurethane.When the soft segment molecular weight was 2,100 g/mol,the hard segment content was 25 wt%,and the BDO:TMP ratio was 9:1,the polyurethane elastomer exhibited high strength（tensile strength of 11.6 MPa）while maintaining good extensibility（elongation at break of approximately 450%）.Furthermore,based on the unsaturated double bonds on the HTPI molecular chains,chemical modification of the polyurethane was performed through vulcanization crosslinking,further enhancing the mechanical strength of the material,especially for linear polyurethane systems.更多还原