Probing Molecular Behavior of Carbonyl Groups at Buried Nylon/Polyolefin Interfaces in Situ.

Nylon and maleic anhydride (MAH)-grafted polyolefin-based thin co-extruded multilayer films are widely used in packaging applications encountered in daily life. The molecular structure of the nylon/MAH-grafted polyolefin buried interface and molecular bonding between these two chemically dissimilar layers are thought to play an important role in achieving packaging structures with good adhesion. Here, the molecular bonds present at a nylon/maleic anhydride (MAH)-grafted polyethylene buried interface were systematically examined in situ for the first time using sum frequency generation (SFG) vibrational spectroscopy. The carbonyl stretching frequency region of the SFG spectra of a nylon/MAH-grafted polyethylene buried interface showed the presence of hydrolyzed MAH groups grafted to the polyethylene chain and very low levels of unreacted MAH enriched at the buried interface. The ability of SFG to detect these molecular species at the buried interface yields important understanding of the interfacial molecular structure and provides the basis for subsequent in situ studies of the bonding reaction between the grafted MAH and nylon directly at the interface. This understanding may guide the design of multilayer films with improved properties such as enhanced adhesion between polymer layers. The approach used in this study is general and is applicable to study the molecular characteristics of other buried interfaces of significance, such as buried interfaces involving polymers in solar cells, polymer semiconductors, and batteries. Nylon impact modification is another area of interest where the interaction between the MAH-grafted elastomer and the continuous phase of nylon is important.

Observing a Chemical Reaction at a Buried Solid/Solid Interface in Situ.

Chemical reactions are the most important phenomena in chemistry. However, chemical reactions at buried solid/solid interfaces are very difficult to study in situ. In this research, the chemical reaction between two solid polymer materials, a nylon film and a maleic anhydride (MAH) grafted poly(ethylene-octene) (MAHgEO) sample, was directly analyzed at the buried nylon/MAHgEO interface at the molecular level in real time and in situ, using surface and interface sensitive sum-frequency generation (SFG) vibrational spectroscopy. Disappearance of nylon signals indicated a chemical reaction between amine and hydrolyzed amide groups of nylon and MAH groups on the MAHgEO at the buried interface. The appearance of SFG signals from reaction products was also observed at the buried nylon/MAHgEO interface. The mechanism of the observed interfacial reaction was further analyzed. Temperature-dependent SFG experiments were performed to measure the activation energy of the interfacial reaction, enabling a comparison with that reported for the bulk materials. The interfacial chemical reaction between nylon and MAHgEO greatly improved the adhesion of these dissimilar materials. The detailed analysis of a chemical reaction between two polymers at the polymer/polymer buried interface underscores the utility of SFG as a powerful analytical tool to build understanding of buried interfaces and to accelerate the design of interfacial structures with desired properties.

Structures and Adhesion Properties at Polyethylene/Silica and Polyethylene/Nylon Interfaces.

The molecular structures of buried interfaces of maleic anhydride grafted and ungrafted polyethylene films with silica and nylon surfaces were studied in situ using sum-frequency generation (SFG) vibrational spectroscopy. Grafting maleic anhydride to polyethylene altered the molecular structures at buried interfaces, including changing the orientation of polymer methylene groups and resulting in the presence of C═O groups at silica interfaces. These molecular level changes are correlated with enhanced adhesion properties, with ordered C═O groups and in-plane orientation of the methylene groups associated with higher levels of adhesion. While improved adhesion was observed for grafted polyethylene at the nylon interface, no C═O groups were detected at the interface using SFG, for films thermally treated at 185 °C. In this case, either no C═O groups are present at the interface or they are disordered; the latter explanation is more likely, considering the observed improvement in adhesion.

Leukemia cutis (involving chronic lymphocytic leukemia) within excisional specimens: a series of 6 cases.

We present 6 cases of chronic lymphocytic leukemia (CLL) that incidentally involved 6 excisional specimens for biopsy-proven carcinoma. CLL was notably absent from all 5 biopsies that were available for review. In 2 of 6 cases, this was the patients' initial presentation of CLL. Five of 6 cases involved routine paraffin-embedded tissue specimens and 1 case involved frozen tissue sections from a Mohs surgical procedure. The mean age range of the patients was 84 years. Only one of 5 patients in which we have follow-up data, died of a CLL-related cause at the time of this submission (mean follow-up 19.8 months). On histologic examination, the most common pattern of involvement by CLL (as seen in 4 of the 6 cases) was a dense, nodular, and superficial and deep perivascular, periadnexal, and perineural infiltrate beneath the fibrosing granulation tissue of the prior biopsy site. The infiltrate involved the upper and deep reticular dermis and subcutaneous fat. The remaining 2 cases demonstrated a novel finding of a subtle infiltration of leukemic cells among extravasated red blood cells within the mid and deep reticular dermis. In all cases, leukemic cells were present as tightly packed, small, monomorphous, hyperchromatic lymphocytes and 1 case demonstrated a proliferation center. Immunohistochemical stains were performed on 3 of 6 cases, and the leukemic cells were CD5/CD20/CD23/CD3. This case series raises awareness that CLL can incidentally involve dermatopathology specimens and occasionally be the initial presentation of the patients' systemic illness. This series also highlights the unique histologic patterns of CLL in the skin, one of which has not been previously described, and illustrates how these patterns are distinct from the typical interstitial infiltration seen in other cases of leukemia cutis.