Synthesis, Characterization, and Structural Investigations of Poly(ethyl acrylate)-l-polyisobutylene Bicomponent Conetwork

Abstract

A new bicomponent conetwork, poly(ethyl acrylate)-linked-polyisobutylene (PEtA-l-PIB), was synthesized by radical copolymerization of equal amounts of telechelic α,ω-dimethacrylic PIB (MA−PIB−MA, M n/(kg/mol) = 11.2, M w/M n = 1.12, and MA/chain = 2.0) obtained via quasi-living carbocationic polymerization and ethyl acrylate in 10% solution for each component in a common solvent, tetrahydrofuran, followed by extraction and drying. Low amounts of extractables (2.5% in acetone and 4.6% in hexane) and nearly theoretical composition (51% PEtA and 49% PIB) of the resulting conetwork indicate efficient network formation; i.e., this new conetwork is composed of PIB chains connected at each end to two PEtA chains. DSC experiments gave close to literature value T g's (−68 °C for PIB and −22 °C for PEtA), indicating a segregated morphology in this conetwork. In contrast to reported results for similar conetworks containing PIB and other polymers with polar groups, surface analysis with XPS found no significant difference in surface and bulk compositions in PEtA-l-PIB. For the first time in the field of bicomponent segmented conetworks, the structure of a conetwork was investigated by small-angle neutron scattering (SANS) in both the relaxed and strained states. Two correlation peaks were observed at q*/Å-1 = 0.035 and at 3q*. The measured value of q* is less by more than a factor of 2 than that predicted by de Gennes for random bicomponent (“grafted”) networks. The macroscopically homogeneous conetwork is characterized by nanoscale local layered like segregation with a correlation length of 445 Å and periodicity of 180 Å. This structure does not deform affinely with the macroscopic deformation. The measured modulus is in excellent agreement with an affine network prediction assuming that each MA−PIB−MA chain gives rise to three elastic strands in the network.

Can Nonpolar Polyisobutylenes be Measured by Electrospray Ionization Mass Spectrometry? Anion-Attachment Proved to be an Appropriate Method

“…Polyisobutylenes (PIBs) with different end-groups including chlorine, exoolefin, hydroxyl, and methyl prepared from aliphatic and aromatic initiators were studied by electrospray ionization mass spectrometry (ESI-MS). Independently of the end-groups, presence or absence of aromatic initiator moiety, these PIB derivatives were capable of forming adduct ions with NO 3 -and Cl -ions, thus allowing the direct characterization of these compounds in the negative ion mode of ESI-MS. To obtain [PIB + NO 3 ] -and [PIB + Cl] -adduct ions with appreciable intensities, addition of polar solvents such as acetone, 2-propanol, or ethanol to the dichloromethane solution of PIBs was necessary. Furthermore, increasing both the polarity (by increasing the acetone content) and the ion-source temperature give rise to enhanced intensities for both [PIB + NO 3 ] -and [PIB + Cl] -ions.…”

“…Independently of the end-groups, presence or absence of aromatic initiator moiety, these PIB derivatives were capable of forming adduct ions with NO 3 -and Cl -ions, thus allowing the direct characterization of these compounds in the negative ion mode of ESI-MS. To obtain [PIB + NO 3 ] -and [PIB + Cl] -adduct ions with appreciable intensities, addition of polar solvents such as acetone, 2-propanol, or ethanol to the dichloromethane solution of PIBs was necessary. Furthermore, increasing both the polarity (by increasing the acetone content) and the ion-source temperature give rise to enhanced intensities for both [PIB + NO 3 ] -and [PIB + Cl] -ions. Energy-dependent collision induced dissociation studies (CID) revealed that increasing the collision voltages resulted in the shift of the apparent molecular masses to higher ones.…”

“…In addition, Density Functional Theory calculations were performed to gain insights into the nature of the interactions between the highly non-polar PIB chains and anions NO 3 -and Cl -as well as to Introduction P olyisobutylenes (PIBs) are nonpolar hydrocarbon polymers produced only by cationic polymerization of isobutylene [1]. Owing to their hydrophobicity, excellent chemical resistance, and biocompatibility, PIBs find applications in many fields including coatings, lubricants, sealants [1], as well as biomaterials for various biomedical applications [2].…”

“…Low molecular weight PIBs are also frequently used as building blocks for preparation of various amphiphilic block copolymers and co-networks. The characterization of molecular weights and end-groups of these blocks are essential for the synthesis of polymeric materials with well-defined structure and architecture [2][3][4][5][6]. Mass spectrometry-based analyses, especially those based on soft ionization technique such as matrix-assisted laser desorption ionization (MALDI-MS) [7,8] and electrospray ionization mass spectrometry (ESI-MS) [9], have become very popular for the determination of molecular weight and end-groups of different polymer classes [10,11].…”

“…Here we present a more general approach for the characterization of low molecular weight PIBs by ESI-MS, which is based on the adduct ion formation of PIBs with nitrate and chloride ions. Since the anions (NO 3 -and Cl -), as will be shown by means of Density Functional Theory (DFT) calculations, attach to the partially positively charged hydrogen atoms of PIBs, the end-group does not affect significantly the resulting ESI-MS spectra. Thus, using this method, highly nonpolar, low molecular weight PIBs with fully saturated bonds can be analyzed.…”