Spaghetti model

More recently, a spaghetti model for a swollen matrix was developed to provide mechanistic understanding of the complex release process (Fig. 4.4). This model treats polymer erosion as diffusion of polymer across a diffusion layer adjacent to the gel layer.19,20 Thus two competitive diffusional processes contribute to overall drug release diffusion of polymer across the diffusion layer and diffusion of drug across the gel layer. Two parameters have been identified to characterize their relative contributions. Polymer disentanglement concentration Cp>dis gauges the... 

Solubility enhancement. Developing CR formulations of poorly soluble drugs could be challenging at time, yet there are some benefits. For moderately insoluble compounds, the corresponding release of drug molecules was found to be similar to that of HPMC.47 As discussed earlier, it can be straightforward to develop hydrophilic matrices for such molecules to achieve zero-order release because polymer release now can be calculated accurately based on the spaghetti model. 

The spaghetti model, for example, predicts the density of the amorphous polymer to be about 65% of that of the crystalline polymer. A value of 85%-95% is experimentally found (see Table 5-3). Thus, it is concluded that a certain degree of order must prevail in the amorphous state, for example, as short parallel arranged lengths of chain or segments. 

However, many polymer scientists have been highly concerned with the density of polymers (332). For many common polymers the density of the amorphous phase is approximately 0.85 to 0.95 that of the crystalline phase (3,10). Returning to the spaghetti model, some scientists think that the polymer chains have to be organized more or less parallel over short distances, or the experimental densities cannot be attained. Others (32) have pointed out that different statistical methods of calculation lead, in fact, to satisfactory agreement between the experimental densities and a more random arrangement of the chains. 

Spaghetti model Model for an amorphous polymer with long chains entangled around each other dates from early days of polymer science, when this structure was unfamiliar 1.5,1.6... 

The ultimate goal in reaction modeling is to discover the overall reaction that occurs within a system. Strangely, whereas the results of nearly every published study involving reaction modeling are presented in a spaghetti diagram (see, e.g., Fig. 13.1), few papers report the overall reaction. For this reason, some of the most... 

Earlier we developed a model for a polymer chain by using a long strand of beads. We could also choose other one-dimensional chain models, such as spaghetti noodles or strands of Easter basket grass. Based on their diam-... 

Amorphous polymers are those whose chains show no order. They exist in entangled random coils. We have used a plate of spaghetti or a bag of Easter basket grass as crude models for amorphous polymers. Note that, based on their diameters, neither the noodles nor the paper or plastic strands are nearly long enough to represent a polymer chain. However, they become physically entangled when mixed together. 

This diagram has been described as looking like a plate of spaghetti with its interconnecting lines between elements of the model. Each element is fathomable and modelable, and therefore relatively simple, but the overall appearance seems to be complex. 

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