Laser-Induced Polymeric Film and Aerosol Particle Formations from Gaseous Molecules.

固体聚合物材料，如薄膜和气溶胶颗粒直接由气态有机分子暴露在N_2激光。从气态丙烯酸甲酯（MA）中，选择性地在辐照容器的石英窗上形成聚合膜。称重测得的产品收率与激光照射时间成正比，与激光强度的次幂大致成正比。沉积膜的红外光谱与市面上可买到的聚丙烯酸甲酯的红外光谱吻合较好，表明自由基是由气相中的两个光子吸收产生的，并且在激光照射下沉积膜表面没有分解成碎片。在N_2激光照射下，MA和丙烯醛（AC）的气体混合物产生固体聚合物薄膜和沉积气溶胶颗粒。沉积膜和沉积颗粒的红外光谱均具有聚丙烯酸甲酯和丙烯醛聚合物的特征，表明产物均由MA和AC聚合物组成。对于MA和AC的气体混合物，成膜过程比气溶胶颗粒的形成更有效。在N_2激光照射下，气态MA和二硫化碳（CS_2）的混合物主要产生沉积气溶胶颗粒。沉积气溶胶颗粒呈球形，平均直径为-0.3 μ m，具有聚丙烯酸甲酯的红外光谱特征，表明MA被聚合到CS_2产生的气溶胶中。通过该研究，我们可以在激光的照射下直接从气体分子中制备新的复合薄膜和气溶胶颗粒。化学成分和颗粒直径也与样品压力、激光强度和照射时间有关。这些发现给我们提供了一种控制新型固体材料的物理和化学性质的方法。

Solid polymeric materials such as thin films and aerosol particles were produced directly from gaseous organic molecules upon the exposure to an N_2 laser light. From gaseous methyl acrylate (MA), polymeric film was formed selectively on a quartz window of the irradiation vessel. The product yield measured by weighing is proportional to the irradiation time of laser light, and is roughly proportional to the second power of the laser intensity. IR spectrum of the deposited film coincides well with the one of poly(methyl acrylate) commercially available, indicating that radical species is produced by two photon absorption in the vapor phase and also on the surface of the deposited film without decomposing into fragments under laser light irradiation.Upon the exposure to an N_2 laser light, gaseous mixture of MA and acrolein (AC) produced both a solid polymeric film and sedimental aerosol particles. IR spectra of both the deposited film and sedimental particle have bands characteristic of poly(methyl acrylate) and acrolein polymer, indicating that both products are composed of MA and AC polymers. For gaseous mixture of MA and AC, film formation process is more efficient than the aerosol particle formation.Gaseous mixture of MA and carbon disulfide (CS_2) produced mainly sedimental aerosol particles upon the exposure to an N_2 laser light. Sedimental aerosol particles are spherical with a mean diameter of -0.3 mum, and has IR bands characteristic of poly(methyl acrylate), indicating that MA is polymerized into the aerosol produced from CS_2.From this research, we could produce new composite films and aerosol particles directly from gaseous molecules under the irradiation of laser light. Chemical composition and particle diameter were also found to depend on sample pressure, laser intensity, and irradiation time. These findings give us a way to control the physical and chemical properties of new solid materials.