This study investigates alginate-chitosan polyelectrolyte complexes (PECs) in the form of a film, a precipitate, as well as a layer-by-layer (LbL) assembly. The focus of this study is to fully characterize, using the complementary techniques of Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) in combination with solution stability evaluation, the interactions between alginate and chitosan in the PECs. In the FTIR spectra, no significant change in the band position of the two carbonyl vibrations from alginate occurs upon interaction with different ionic species. However, protonation of the carboxylate group causes a new band to appear at 1710 cm(-1), as anticipated. Partial protonation of the amine group of chitosan causes the appearance of one new band ( approximately 1530 cm(-1)) due to one of the -NH3+ vibrational modes (the other mode overlaps the amide I band). Importantly, the position of the two main bands in the spectral region of interest in partly protonated chitosan films is not dependent on the extent of protonation. XPS N 1s narrow scans can, however, be used to assess the degree of amine protonation. In our alginate-chitosan film, precipitate, and LbL assembly, the bands observed in the FTIR correspond to the species -COO- and -NH3+, but their position is not different from each of the single components. Thus, the conclusion of the study is that FTIR cannot be used directly to identify the presence of PECs. However, in combination with XPS (survey and narrow N 1s scans) and solution stability evaluation, a more complete description of the structure can be obtained. This conclusion challenges the assignment of FTIR spectra in the literature.

Amine functionalities were introduced onto the surface of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films by applying radio frequency ammonia plasma treatment and wet ethylenediamine treatment. The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS) for chemical composition and Raman microspectroscopy for the spatial distribution of the chemical moieties. The relative amount of amine functionalities introduced onto the PHBV surface was determined by exposing the treated films to the vapor of trifluoromethylbenzaldehyde (TFBA) prior to XPS analysis. The highest amount of amino groups on the PHBV surface could be introduced by use of ammonia plasma at short treatment times of 5 and 10 s, but no effect of plasma power within the range of 2.5-20 W was observed. Ethylenediamine treatment yielded fewer surface amino groups, and in addition an increase in crystallinity as well as degradation of PHBV was evident from Fourier transform infrared spectroscopy. Raman maps showed that the coverage of amino groups on the PHBV surfaces was patchy with large areas having no amine functionalities.

The interactions of block copolymers with surfaces can be controlled by coating those surfaces with appropriate statistical copolymers. Usually, a statistical copolymer comprised of monomer units identical to those of the block copolymer is used; that is, typically a poly(styrene)-stat-poly(methyl methacrylate) (PS-stat-PMMA) is used to direct the alignment of poly(styrene)-block-poly(methyl methacrylate) (PS-block-PMMA), and poly(styrene)-stat-poly(2-vinylpyridine) (PS-stat-P2VP) has been used for poly(styrene)-block-poly(2-vinylpyridine) (PS-block-P2VP). Reports of controlling the orientation of block copolymers with statistical copolymers with a dissimilar composition are limited. Here, we demonstrate that this method can be further extended to show that PS-stat-PMMA can be used to control the wetting properties of poly(styrene)-block-poly(D,L-lactide) (PS-block-PDLA). Surfaces were modified with a series of cross-linked PS-stat-PMMA-stat-glycidyl methacrylate terpolymers, and the surface chemistries and energies were assessed using angle-dependent X-ray photoelectron spectroscopy and the two-liquid harmonic method, respectively. From these experiments, an expected neutral compositional window was identified for symmetrical PS-block-PDLA. Moreover, high-resolution SEM, AD-XPS, and grazing-incidence SAXS measurements were used to evaluate the morphology of PS-block-PDLA as a function of the surface composition of the underlying cross-linked copolymer films, and the neutral composition was found to range from 32 to 38 mol % of PS, in the bulk polymer. Ultimately, we demonstrated the determination of nonpreferential surface compositions that allow the self-assembly of lamellae with sizes in the sub-10 nm regime that are oriented perpendicular to the substrate. These findings have important implications for the use of PS-block-PDLA block copolymers in directed self-assembly, most specifically in advanced lithographic processes.

2-Hydroxyethyl methacrylate has been polymerized in methanol using activators regenerated by electron transfer (ARGET) atom transfer radical polymerization (ATRP), to produce water-soluble poly(2-hydroxyethyl methacrylate) (PHEMA). The various parameters that determine control of the living polymerization have been explored. Using the Cu(II)/TPMA catalyst system (TPMA ¼ tris(2-pyridylmethyl)amine), controlled polymerization was achieved with Cu concentrations as low as 50 ppm relative to HEMA, with a [TPMA]/[Cu(II)] ratio of 5. Use of hydrazine as the reducing agent generally gave better control of polymerization than use of ascorbic acid. The polymerization conditions were tolerant of small amounts of air, and colorless polymers were easily isolated by simple precipitation and washing steps. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4084][4085][4086][4087][4088][4089][4090][4091][4092] 2010