增加螺旋聚合物的分子量参数,通过在性溶剂中的聚合
Simon J Holder1, Mariliz Achilleos, Richard G Jones
1Functional Materials Group, School of Physical Sciences, University of Kent, Canterbury, Kent CT2 7NH, UK. S.J.Holder@kent.ac.uk
Journal of the American Chemical Society
|September 21, 2006
概括
状溶剂通过在聚合过程中改变螺旋链感应来影响聚合物的分子量. 这项研究表明,与拉塞米混合物相比,奇拉溶剂显著增加了聚甲基基的分子量.
科学领域:
- 聚合物化学 聚合物化学
- 奇拉化学 奇拉化学
- 材料科学 材料科学 材料科学
背景情况:
- 已知化溶剂会影响化学反应中的立体化学.
- 性溶剂对聚合动力学和分子量分布的影响不太清楚.
- 聚合物链中的螺旋螺杆感应 (P和M) 可以影响材料特性.
研究的目的:
- 为了研究性溶剂对聚合物的分子量分布的影响.
- 为了证明性溶剂如何扰乱增长的聚合物链的螺旋螺杆感官.
- 为了建立一种新的链接,介质溶剂的使用和改变的聚合结局之间.
主要方法:
- 聚甲基基 (PMPS) 的沃茨型合成.
- 在 (R) - 烯和 (S) - 烯溶剂中进行的聚合.
- 合成的PMPS的比较在奇拉与racemic (R/S) -limonene中.
- 分析所得到的聚合物的重量平均分子量 (Mw).
主要成果:
- 在奇拉烯中合成的PMPS的重量平均分子量 (Mw) 约为80,000.
- 在种族性 (R/S) - 中合成的PMPS的Mw明显较低,平均为39,200.
- 已证实,在生长的聚合物链中,状溶剂会扰乱P和M螺旋螺杆感官的平衡.
- 这种扰动减少了聚合过程中关键终结步骤的速度.
结论:
- 化溶剂可以显著影响聚合物的分子量分布.
- 这种效应归因于沿着聚合物链的螺旋螺杆感应器的干扰.
- 这一发现首次证明了奇拉溶剂在聚合过程中影响分子重量参数,而不是战术效应.
相关概念视频
01:01Polymers: Defining Molecular Weight
Unlike small molecules with definite molecular weights, polymers are a mixture of individual polymer chains of varying lengths, each with a unique molecular weight. So, the molecular weight of a polymer is expressed as an average value based on the average size of the polymer chains. The two most common forms of averages used for polymers are the number average molecular weight and weight average molecular weight.
The number average molecular weight (Mn) is the summation of the number...
The number average molecular weight (Mn) is the summation of the number...
01:10Polymers: Molecular Weight Distribution
For any given polymer, the weight average molecular weight (Mw) is higher than, if not equal to, the number average molecular weight (Mn). The only situation in which the weight average molecular weight and the number average molecular weight are equal is when a polymer consists only of chains with equal molecular weight. However, this never happens in a synthetic polymer, since it is difficult to control the polymerization process up to a molecular level with accuracy to a hundred percent.
01:08Molecular Weight of Step-Growth Polymers
Step growth polymerization involves bi or multifunctional monomers. Bifunctional monomers react to form linear step growth polymers, whereas multifunctional monomers react to form non-linear or branched polymers.
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
As the step-growth polymerization involves step-wise condensation of monomers, the molecular weight also builds up eventually. Consequently, high molecular weight polymers are obtained at the late stages of the polymerization, where 99% of monomers have been consumed.
The extent of the...
01:24Determination of Molar Masses of Polymers I
Polymerization produces macromolecules with a range of chain lengths due to the random nature of molecular growth processes. As chains form and terminate at different stages, a single polymer sample contains molecules of varying sizes rather than a uniform structure. This variability is described using average molar masses and distribution-related parameters, which together provide a comprehensive understanding of polymer characteristics.The distribution of molar masses plays a critical role in...
01:27Determination of Molar Masses of Polymers II
Polymer samples typically consist of macromolecular chains with a distribution of lengths, resulting in a range of molar masses rather than a single discrete value. Conventional descriptors such as the number-average molar mass and weight-average molar mass quantify this distribution but do not fully capture polymer behavior in solution..The viscosity-average molar mass provides a more realistic description of polymer behavior in solution because it accounts for the enhanced contribution of...