Early Stages of Styrene−Isoprene Copolymerization in Gas Phase Clusters Probed by Resonance Enhanced Multiphoton Ionization

Abstract

We present direct evidence for the formation of the covalent bonded styrene (isoprene)(2) oligomer and the isoprene dimer ions following resonance ionization of the gas phase styrene-isoprene binary clusters. The application of resonance ionization to study polymerization reactions in clusters provides new information on the structure and mechanism of formation of the early stages of polymerization and holds considerable promise for the discovery of new initiation mechanisms and for the development of novel materials with unique properties.

Formation of Nitrogen-Containing Polycyclic Cations by Gas-Phase and Intracluster Reactions of Acetylene with the Pyridinium and Pyrimidinium Ions

“…In the gas phase at low pressures, ion–molecule reactions may proceed via an elimination mechanism. ,, However, in the same systems at high pressure, the ionic intermediates may be stabilized, and addition without elimination may occur. In clusters, both elimination and addition reactions can take place resulting in product ion distributions that reflect both the stability of the covalent adducts and the kinetics of the reactions. ,,,− Therefore, sequential polymerization and growth involving several addition and/or elimination steps can occur following the ionization of isolated molecular clusters. ,,,− This occurs because the energy released from the condensation reactions can be efficiently dissipated by fast evaporation (boiling off) of nonreacting monomers from the cluster. The competition between the condensation reactions leading to the growth of the covalent ion and monomer evaporation resulting in depleting the monomer concentration in the cluster can control the ultimate size that the covalent ion can reach in the cluster.…”

“…To study the intracluster reactions, we generated (pyridine) n (acetylene) m binary clusters using the supersonic beam expansion technique. ,,− One of the major questions that must be addressed is whether the resulting ions are covalent adducts formed by intracluster reactions, or simply cluster ions held together by electrostatic ion-induced dipole forces. To answer this question, we used a combination of ion dissociation and ion mobility measurements assisted by DFT structural calculations of possible product ions as described below.…”

Polymerization in the Gas Phase, in Clusters, and on Nanoparticle Surfaces

“…Several groups have developed laser and mass spectrometric methods to study anionic, cationic, and metal ion-induced intracluster polymerization. [8][9][10][11][13][14][15][20][21][22][23][24][25]29,31,[34][35][36][37][40][41][42]44,46 Other groups have developed novel approaches to determine the gas-phase conformations of a variety of oligomers and polymers including biopolymers, synthetic polymers, metal ion cationized polymers, and photoluminescence-conjugated polymers. [53][54][55][56][57][58][59][60][61] Our group has focused on studying the early stages of cationic and radical cation polymerization within clusters of a variety of unsaturated organic molecules.…”

“…[53][54][55][56][57][58][59][60][61] Our group has focused on studying the early stages of cationic and radical cation polymerization within clusters of a variety of unsaturated organic molecules. 8,9,15,18,[22][23][24][25]28,29,34,41,42,44,46 In this Account, we describe several examples of gas-phase and cluster polymerization studies with special emphasis on understanding the reaction mechanisms, the structural identification of oligomers formed in the early stages of polymerization and the incorporation of nanoparticles within polymeric materials formed by gas-phase processes.…”

“…Most of the current knowledge of polymerization reactions and polymer properties comes from experiments dealing with bulk liquids or solutions. – This is because these are the preferred media for many industrial and laboratory polymerization processes. However, a number of important phenomena, unique structures, and novel properties may exist for gas-phase and cluster polymerization. – In this regime, the structure of the growing polymer may change dramatically and the rate coefficient may vary significantly upon the addition of a single monomer molecule. These changes would be reflected in the properties of the oligomers.…”