梯度折射率聚合物细棒的制备和数学模拟

DISTRIBUTION OF POLYMER CONCENTRATION IN GRADED REFRACTIVE INDEX POLYMER OPTICAL FIBER PREFORM PREPAREING PROCESS

在聚甲基丙烯酸甲酯 (Poly(methylmethacrylate) ,PMMA)管中 ,加入单体甲基丙烯酸甲酯 (Methylmethacrylate ,MMA)和另一种高折射率的掺杂剂溴苯 (Bromobenzene ,BB) ,用界面凝胶均聚合方法制备了梯度折射率聚合物光纤预制棒 .这种光纤预制棒的梯度折射率是通过具有不同折射率的分子扩散而形成的 .通过对界面凝胶聚合过程的描述 ,该工作讨论了预制棒中聚合物的浓度分布及边界条件的假设 .并根据自由体积理论对其折射率分布进行理论模拟 .将得到的折射率抛物线分布与实验结果进行对比 ,结果表明聚合浓度的分布为ω =a(r/R) 2 +b时 ,理论预计的光纤预制棒的折射率分布与实验结果有着较好的符合 .同时 。

Graded refractive index polymer optical fibers (GI POF) have received extensive interest due to their potential application in optical communication.GI POF can be prepared by drawing preforms into fiber under suitable condition.A graded refractive index poly(methyl methacrylate) (PMMA) preform has been made by an interfacial\|gel polymerization procedure,in which polymerization was performed in a PMMA tube and a dopant,bromobenzene(BB),was used as a higher refractive index component.The graded refractive index was formed by the diffusion of the molecules.At a certain time,according to the free\|volume theory of self\|diffusion the radial distribution of the dopant remains unchanging as the available free volume is fixed at each point and the polymerization continues.A model of forming the graded refractive index is established by the theoretical application in a high\|conversion polymerization system.Through describing the process of interfacial\|gel polymerization,the distribution of the polymer concentration at the radical direction of the tube was assumed to be ω=a(r/R)\+2+b .The boundary conditions of the polymer concentration were discussed in order to get the simulating refractive index distribution of the GI POF preform.Diffusion coefficients of the monomer and dopant were calculated.The concentration distributions of the molecules were related to their diffusion coefficients respectively.Under these conditions,according to Lorentz and Lorenze formulation a quadratic distribution of refractive index on the radial direction of the preform is simulated.The theoretical simulating result is in good agreement with the experimental result.The effect of MMA/BB ratio on the distribution of the polymer concentration was also discussed.For polymerization systems with different ratios of MMA/BB,the polymer concentration distributions and the boundary conditions would be differnet.