The properties of thin supported polymer films can be dramatically impacted by the substrate upon which it resides. A simple way to alter the properties of the substrate (chemistry, rigidity, dynamics) is by coating it with an immiscible polymer. Here, we describe how ultrathin (ca. 2 nm) hydrophilic polymer layers of poly(acrylic acid) and poly(styrene sulfonate) (PSS) impact the aging behavior and the residual stress in thin films of poly(butylnorbornene‐
The physical aging behavior, time‐dependent densification, of thin polystyrene (PS) films supported on silicon are investigated using ellipsometry for a large range of molecular weights (MWs) from
- Award ID(s):
- 1709132
- PAR ID:
- 10461487
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Polymer Science Part B: Polymer Physics
- Volume:
- 57
- Issue:
- 18
- ISSN:
- 0887-6266
- Page Range / eLocation ID:
- p. 1224-1238
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
ABSTRACT ran ‐hydroxyhexafluoroisopropyl norbornene) (BuNB‐r ‐HFANB). The aging rate decreases as the film thickness (h ) is decreased, but the extent of this change depends on the adjacent layer. Even for the thickest films (h > 500 nm), there is a decrease in the aging rate at 100 °C when BuNB‐r ‐HFANB is in contact with PSS. In an effort to understand the origins of these differences in the aging behavior, the elastic modulus and residual stress (σR) in the films were determined by wrinkling as a function of aging time. The change in the elastic modulus during aging does not appear to be directly correlated with the densification or expansion of the films, but the aging rates appear to roughly scale ash σR1/3. These results illustrate that the physical aging of thin polymer films can be altered by adjacent polymers. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2019 ,57 , 992–1000 -
more » « less
ABSTRACT The isothermal structural relaxation (densification) of a family of glassy polynorbornene films with high glass transition temperatures (
T g > 613 K) is assessed via spectroscopic ellipsometry. Three polymers were examined: poly(butylnorbornene) (BuNB), poly(hydroxyhexafluoroisopropyl norbornene) (HFANB), and their random copolymer, BuNB‐r ‐HFANB. The effective aging rate,β (T ), of thick (∼1.2 μm) spun cast films of BuNB‐r ‐HFANB is approximately 10−3over a wide temperature window (0.49 <T /T g < 0.68). At higher temperatures, these polymers undergo reactions that more dramatically decrease the film thickness, which prohibits erasing the process history by annealing aboveT g. The aging rate for thick BuNB‐r ‐HFANB films is independent of the casting solvent, which infers that rapid aging is not associated with residual solvent.β (at 373 K) decreases for films thinner than ∼500 nm. However, the isothermal structural relaxation of thin films of BuNB‐r ‐HFANB exhibits nonmonotonic temporal evolution in thickness for films thinner than 115 nm film. The thickness after 18 h of aging at 373 K can be greater than the initial thickness. The rapid aging of these polynorbornene films is attributed to the unusual rapid local dynamics of this class of polymers and demonstrates the potential for unexpected structural relaxations in membranes and thin films of high‐T gpolymers that could impact their performance. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2018 ,56 , 53–61 -
more » « less
ABSTRACT Morphology modulation offers significant control over organic electronic device performance. However, morphology quantification has been rarely carried out
via image analysis. In this work, we designed a MATLAB program to evaluate two key parameters describing morphology of small molecule semiconductor thin films: fractal dimension and film coverage. We then use this program in a case study of meniscus‐guided coating of 2,7‐dioctyl[1]benzothieno[3,2‐b][1]benzothiophene (C8‐BTBT) under various conditions to analyze a diverse and complex morphology set. The evolution of morphology in terms of fractal dimension and film coverage was studied as a function of coating speed. We discovered that combined fractal dimension and film coverage can quantitatively capture the key characteristics of C8‐BTBT thin film morphology; change of these two parameters further inform morphology transition. Furthermore, fractal dimension could potentially shed light on thin film growth mechanisms. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2019 , 57, 1622–1634 -
more » « less
ABSTRACT The thin film phase behavior of ternary blends consisting of symmetric poly(styrene) (PS)‐
b ‐poly(dimethylsiloxane)(PDMS), PS, and PDMS was investigated using X‐ray reflectivity (XRR) and atomic force microscopy (AFM). This system is strongly segregated, and the homopolymers are approximately the same length as the corresponding blocks of the copolymer. The XRR and AFM data are used to quantify changes in domain spacing (L ) and morphology evolution with increasing homopolymer content (ΦH ). In 100 nm thick films, from ΦH = 0 to 0.20, the system maintains a perfect parallel lamellar structure and domains swell as predicted based on theory; however, from ΦH = 0.30 to 0.50, a morphology transition to a “dot pattern” morphology (tentatively identified as perforated lamellae) and mixed morphologies were observed before macrophase separation. In thicker films, dot patterns were observed for a broad range of ΦH before macrophase separation. The absence of the bicontinuous microemulsion phase reported for bulk blends and thin films of perpendicular lamellae and the presence of dot patterns/perforated lamellae are attributed to preferential migration of the PDMS homopolymer to the wetting layers located at the substrate and free air interfaces, which leads to an asymmetric composition within the film and morphology transition. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys.2018 ,56 , 1443–1451 -
more » « less
ABSTRACT This work investigates effects of poly(
γ ‐butyrolactone) (Pγ BL) with different initiation and termination chain ends on five types of materials properties, including thermal stability, thermal transitions, thermal recyclability, hydrolytic degradation, and dynamic mechanical behavior. Four different chain‐end‐capped polymers with similar molecular weights, BnO‐[C(=O)(CH2)3O]n‐R, R = C(=O)Me, C(=O)CH=CH2, C(=O)Ph, and SiMe2CMe3, along with a series of uncapped polymers R′O‐[C(=O)(CH2)3O]n‐H (R′ = Bn, Ph2CHCH2) withM nranging from low (4.95 kg mol−1) to high (83.2 kg mol−1), have been synthesized. The termination chain end R showed a large effect on polymer decomposition temperature and hydrolytic degradation, relative to H. Overall, for those properties sensitive to the chain ends, chain‐end capping renders R‐protected linear Pγ BL behaving much like cyclic Pγ BL. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2018 ,56 , 2271–2279
