The effects of alkyl side chain and spacer lengths and the type of terminal group on the morphology and crystallization of a homologous series of biscarbamates (model compounds for polyurethanes) were investigated. Biscarbamates were synthesized with alkyl side chains of various lengths ranging from C-4 to C-18 and an alkyl spacer group with 12 CH2 units (C-12 spacer) between the two hydrogen bonding motifs. The crystallization and morphological features are compared with the previously studied biscarbamates with a C-6 spacer. As a token example, we also studied a biscarbamate molecule in which the terminal methyl group was replaced by a phenyl group. We stress four important conclusions of the study: (I) A number of studies in the literature found that the longer alkyl spacers reduced the thermal transition temperatures of the molecules, and such behavior was attributed to an increase in the flexibility of the alkyl spacer. However, the results of the present study are to the contrary. With the biscarbamates studied here, the hydrogen-bonding groups on both sides of the C-12 spacer act as "anchors", and the longer spacer does not reduce the melting temperatures compared with those with the C-6 spacer. (2) The melt viscosity measurements show shear-thinning behavior, which has been mostly observed with polysaccharides and hydrogen-bonded polymers. (3) Avrami analysis shows a two-stage crystallization, which is not commonly observed in organic small molecule systems. (4) The phenyl end group does not add another self-assembly code in terms of pi-stacking but acts as a defect. While formation of crystals was observed for biscarbamates with short alkyl side chains with a C-6 spacer, an increase in spacer length to C-12 induces spherulitic morphology. Although the overall sizes of the spherulites are the same for both spacers, the rate of spherulite growth was higher and the crystallization rate was lower with the C-12 spacer compared with the C-6 spacer. In contrast with the biscarbamates containing C-6 spacer previously studied, we find that among the biscarbamates with 12 CH2 units in the spacer the C-12-C-12 molecule shows the minimum spherulite size, spherulite growth rate, and rate of crystallization. The infrared frequency shifts of the N-H group due to hydrogen bonding were used to calculate the N center dot center dot center dot O hydrogen-bonding distance and found to be close to the value observed in the crystal structure of the biscarbamate with a C-6 spacer and C-10 alkyl side chain.